IIBSi? 


PAUL  JL 

I'AV'-    L, 


TEXT-BOOK 


OF 


Z  O  O  L  O  G  Y 


FOR  SCHOOLS  AND  COLLEGES 


BY 

H.  ALLEYM  MCHOLSOX, 

M.D.,  D.Sc.,  M.A.,  PH.D.,  F.K.8.E.,  F.G.S.,  ETC., 

PROFESSOR    OF    NATURAL    HISTORY    AND    BOTANY    IN    UNIVERSITY   COLLEGE,  TORONTO? 
FORMERLY  LECTURER  ON  NATURAL   HISTORY   IN   THE    MEDICAL   SCHOOL  OF  EDIN- 
BURGH; AUTHOR  OF  "MANUAL  OF  ZOOLOGY  FOR  THE  USE  OF  STUDENTS," 
"TEXT-BOOK  OF  GEOLOGY,"  "INTRODUCTORY  TEXT-BOOK  OF 

ZOOLOGY,"    "GEOLOGY   OF  CUMBERLAND  AND 
WESTMORELAND,"   ETC.,   ETC. 


NEW  YOKE: 
D.    APPLETON    AND    COMPANY, 

1,    3,    AND    5   BOND    STREET. 

1884. 


ENTEBED,  according  to  Act  of  Congress,  in  the  year  1871,  by 

D.  APPLETON  &  CO., 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


EDUCA2IOU 


A)  52. 


PREFACE. 


Ix  bringing  out  a  Text-book  of  Natural  History,  intended 
mainly  for  the  use  of  schools,  there  are  a  few  remarks  which 
it  may  be  as  well  to  make  by  way  of  preface,  if  only  to  ex- 
plain the  principles  upon  which  the  work  has  been  written. 

In  the  first  place,  more  space  has  been  devoted,  compara- 
tively speaking,  to  the  Invertebrate  Animals  than  has  usually 
been  the  case  in  introductory  works,  upon  the  belief  that  any 
practical  Zoological  work  likely  to  be  undertaken  by  young 
students  will  certainly  be  in  connection  with  these  rather 
than  with  the  Vertebrate  Animals. 

Secondly,  the  Author  has  devoted  considerable  space  to  a 
discussion  of  the  principles  of  Zoological  classification,  be- 
lieving that  it  is  of  paramount  importance  that  the  student 
should  have  a  clear  idea  of  the  principles  upon  which  the 
Animal  Kingdom  has  been  systematically  divided.  At  the 
same  time,  the  introductory  portion  of  the  work  is  more 
especially  intended  for  the  teacher ;  and  there  is  much  in  it 
that  the  learner  may  perhaps  hardly  understand  till  he  has 
arrived  at  some  clear  idea  of  Natural  History  as  a  whole. 

Thirdly,  while  the  Author  trusts  that  the  style  of  the 
work  will  be  found  clear  and  intelligible,  he  does  not  believe 
in  the  existence  of  any  royal  road  to  learning  in  Natural 
History,  any  more  than  in  any  other  department  of  human 
knowledge.  If  Natural  History  is  ever  to  be  taught  in 

M577G42 


iv  PREFACE. 

schools,  with  any  satisfaction  to  the  teacher,  or  any  profit  to 
the  learner,  it  must  be  taught  as  systematically  and  as  un- 
flinchingly as  Mathematics  and  Greek  have  been  taught  for 
many  generations.  The  Author  is  one  of  those  who  believe 
that  the  time  is  now  approaching,  if  it  be  not  already  here, 
when  the  Natural  Sciences  will  take  their  true  place  in  school 
education,  as  second  to  no  other  branch  of  knowledge,  either 
as  regards  their  intrinsic  value  and  interest,  or  regarded  mere- 
ly as  a  means  of  developing  the  mental  powers.  Acting  upon 
this  belief,  the  Author  has,  therefore,  treated  his  subject  in  a 
purely  scientific  spirit ;  and,  while  avoiding  as  much  as  pos- 
sible the  use  of  technicalities,  he  has  not  endeavored  to  lend 
his  subject  any  false  glitter  or  embellishment ;  firmly  believ- 
ing that  there  is  even  a  certain  mental  training  involved  in 
the  recognition  that  a  strictly  scientific  description  is  not 
without  its  own  charms  and  beauties.  While  the  use  of  tech- 
nical terms  has  been  as  far  as  possible  restricted,  it  is  believed 
that  an  explanation  of  every  unavoidable  term  will  be  found 
in  the  glossary,  or  is  appended  in  the  text. 

Lastly,  the  illustrations,  with  few  exceptions,  have  been 
drawn  on  the  wood  by  the  Author,  and  he  has  thought  it  wise 
to  wholly  eschew  the  use  of  pictorial  illustrations,  as  unneces- 
sary in  a  scientific  work,  however  elementary  it  may  be. 


TABLE    OF    CONTENTS. 


INTRODUCTION. 

Definition  of  Biology  and  Zoology — Characters  of  dead  and  unorganized  bodies — Characters 
of  living  and  organized  bodies — Differences  between  animals  and  plants — Principles  of 
Zoological  classification— The  great  Physiological  Functions— Homology  and  Analogy- 
General  Divisions  of  the  Animal  Kingdom— Invertebrata  and  Vertebrata,  .  Pages  1-24 

CHAPTER  I. 

General  characters  of  the  Protozoa— Classification  of  the  Protozoa— Gregarinidas,  .    p.  25-28 

CHAPTER  II. 

General  characters  and  orders  of  the  Ehizopoda— Anatomy  of  the  Amoebea— Foraminifera— 
Affinities — Distribution  of  the  Foraminifera  in  Space  and  in  Time — Radiolaria — Acan- 
thoinetra3— Polycystina— Thallassicollida— Spongida— Structure  of  a  Sponge— Reproduc- 
tion of  Spongilla— Distribution  of  Sponges  in  space, p.  29^4 

CHAPTER  III. 

General  characters  of  the  Infusoria — Anatomy  of  Paramcecium — Structure  of  Epistylis — 
Orders  of  Infusoria— Distribution  of  Infusoria  in  space — Tabular  view  of  the  divisions 
of  the  Protozoa, p.  45-49 

CHAPTER  IV. 

General  characters  of  the  Ccelenterata — Divisions  of  the  Ccelenterata — General  characters  of 
the  Hydrozoa— General  terminology  of  the  Hydrozoa, p.  50-56 

CHAPTER  V. 

Divisions  of  the  Hydrozoa — Hydroida — Hydrida — Anatomy  of  Hydra — Corynida — Repro- 
duction in  the  Corynida  and  in  the  Hydroid  Zoophytes  generally— Alternation  of  gen- 
erations— Sertularida — Campanularida, p.  57-69 

CHAPTER  VI. 
Siphonophora  or  Oceanic  Hydrozoa— Calycophorida>— Physophoridae,     .  .    p.  70-73 

CHAPTER  VII. 

Discophora  or  Medusidse— Structure  of  Naked-eyed  Medusae— Their  nature,         .    p.  74-7T 


vi  TABLE   OF  CONTENTS. 

CHAPTER   VIII. 

Lucernarida— Hidden-eyed  Medusae— Development  of  Lucernarida— Bhizostomidae— Grap- 
tolitidae, '  .  Pages  78-83 

CHAPTER  IX. 

General  characters  of  the  Actinozoa — Zoantharia — Anatomy  of  a  Sea- Anemone — Zoantharia 
Sclerodermata— Scleroderinic  and  Sclerobasic  Corals— Coral-reefs— Zoantharia  Sclero- 
basica — Alcyonaria — Gorgonidae — Red  Coral — Rugose  Corals — Ctenophora — Anatomy  of 
Pleurobrachia— Tabular  view  of  the  divisions  of  the  Ccelenterata,  .  .  .  p.  84-94 

CHAPTER  X. 

General  characters  of  the  Annuloida — General  characters  of  the  Echinodermata — Divisions 
of  the  Echinodermata— Echinoidea— Anatomy  of  Echinus— Asteroidea— Ophiuroidea— 
Crinoidea— Cystoidea  and  Blastoidea— Holothuroidea, p.  95-10T 

CHAPTER  XI. 

General  characters  of  the  Scolecida — Divisions  of  the  Scolecida — Tseniada — Development  of 
a  Tape-worm — Cystic  worms — Trematoda — Turbellaria — Acanthocephala — Gordiacea — 
Nematoda— Rotifera— Tabular  view  of  the  divisions  of  the  Annuloida,  .  p.  108-117 

CHAPTER  XII. 

General  characters  of  the  Annulosa — Characters  of  the  Anarthropoda — Gephyrea — Annelida 
—Divisions  of  the  Annelida— Hirudinea— Oligochaeta— Tubicola— Errantia,  p.  118-125 

CHAPTER    XIII. 

General  characters  of  the  Arthropoda— Divisions  of  the  Arthropoda,  .        .        .    p.  12C,  127 

CHAPTER    XIV. 

General  characters  of  the  Crustacea — Decapoda — Macrura — Anomura — Brachyura — Isopoda 
— Merostomata— Trilobita— Cladocera,  Copepoda,  and  Ostracoda— Cirripedia—  Appendix 
of  the  remaining  orders  of  Crustaceans,  ........  p.  128-138 

CHAPTER  XV. 

General  characters  of  the  Arachnida— Podosomata— Acarina— Pedipalpi— Araneida, 

p.  189-143 

CHAPTER    XVI. 

General  characters  of  the  Myriapoda— Centipedes— Millipedes    .        .        .       .     p.  144, 145 

CHAPTER  XVII. 

General  characters  and  anatomy  of  Insects— Metamorphoses  of  Insects,     .        .    p.  146-152 

CHAPTER  XVIII. 

Orders  of  Insects— Anoplura— Mallophaga— Thysanura— Hemiptera— Orthoptera— ^"europ- 
tera — Aphaniptera — Diptera — Lepidoptera — Hymenoptera — Strepsiptera — Coleoptera — 
Tabular  view  of  the  divisions  of  the  sub-kingdom  Annulosa,  .  .  .  p.  153-163 


TABLE  OF  CONTENTS.  vii 

CHAPTER    XIX. 

General  characters  of  the  Mollusca — Primary  divisions  of  the  Mollusca,        .    Pages  164-1 6T 

CHAPTER  XX. 

Molluscoida— General  characters  of  the  Polyzoa— General  characters  of  the  Tunicata— Gen- 
eral characters  of  the  Brachiopoda, p.  168-175 

CHAPTER  XXI. 

Classes  of  the  Mollusca  Proper— General  characters  of  the  Lamellibranchiata— General  char- 
acters of  the  Gasteropoda— Nudibranchiata— Heteropoda— Air-breathing  Gasteropods— 
Pteropoda, p.  176-186 

CHAPTER  XXII. 

General  characters  of  the  Cephalopoda — Reproductive  process  hi  the  Cuttle-fishes — Shell  of 
the  Cephalopoda — Dibranchiata — Tetrabranchiata — Orthocerata — Ammonites — Tabular 
view  of  the  main  divisions  of  the  Mollusca, p.  187-194 

CHAPTER  XXIII. 

General  characters  of  the  Vertebrata — Skeleton  of  Vertebrates — Structure  of  a  Vertebra — 
Vertebral  column — Limbs  of  Vertebrates — Digestive  system — Circulatory  system — Re- 
spiratory system— Nervous  system— Reproduction— Primary  divisions— Ichthyopsida— 
Sauropsida— Mammalia, p.  195-205 

CHAPTER  XXIV. 

General  characters  of  the  Fishes— Scales— Endoskeleton— Limbs— Tail— Digestive  system— 
Circulation— Respiration— Nervous  system— Organs  of  hearing  and  smell— Reproduc- 
tion, .......  .p.  206-213 

CHAPTER  XXV. 

Orders  of  Fishes— Pharyngobranchii— Marsipobranchii— Teleostei— Sub-orders  of  the  Tele- 
ostei — Ganoidei — Elasmobranchii — Sub-orders  of  the  Elasmobranchii — Dipnoi, 

p.  214-224 

CHAPTER   XXVI. 

General  characters  of  the  Amphibia — Orders  of  the  Amphibia — Ophiomorpha — Urodela — 
Anoura— Labyrinthodoutia, p.  225-233 

CHAPTER  XXVII. 

General  characters  of  the  Reptilia— Circulatory  and  Respiratory  systems— Divisions, 

p.  234-237 

CHAPTER  XXVIII. 

Orders  of  Reptilia— Chelonia— Ophidia— Lacertilia— Crocodffia— Ichthyopterygia— Saurop- 
terygia— Pterosauria, p.  238-252 

CHAPTER  XXIX. 

General  characters  of  the  Class  Aves— Feathers— Vertebral  column— Anterior  extremity 
and  pectoral  arch — posterior  extremity  and  pelvic  arch — Digestive  system — Respira- 


viii  TABLE   OF  CONTENTS. 

tion— Circulatory  system— Nervous   system — Organs    of    the    Senses— Migrations  of 
Birds, Pages  253-264 

CHAPTER  XXX. 

Divisions  of  Aves  —  Natatores —  Grallatores — Cursores — Easores — Scansores — Insessores 

Eaptores — Saururae, p.  265-279 

CHAPTER  XXXI. 

General  characters  of  the  Class  Mammalia— Skeleton— Teeth— Dental  formula— Digestive 
system — Heart — Lungs — Nervous  system — Integumentary  appendages — Development 
—Primary  divisions, p.  280-287 

CHAPTER  XXXII. 

Orders  of  Mammalia— Monotremata—Marsupialia— Edentata— Sirenia— Cetacea— Ungulata 
— Hyracoidea — Proboscidea-^Carnivora — Rodentia — Cheiroptera  —  Insectivora  —  Quad- 
rumana— Birnana, .  p.  288-320 


LIST  OF  ILLUSTEATIO^S. 


1.  Diagram  representing  Transverse  Sections  of  the  Invertebrata  and 

Vertebrata,        .  16 

2.  Gregarina  of  the  Earth-worm,            .....  28 

3.  Morphology  of  Ehizopoda,             .            .            .            .            .  .30 

4.  Morphology  of  Foraminifera,             .....  34 

5.  Nummulites  Icevigatus,       .......       38 

6.  AcantJiometra  and  Haliomma,             .....  39 

7.  Morphology  of  Thalassicollida,     .            .            .            .            .  .40 

8.  Diagrammatic  Section  of  Fresh- water  Sponge,        ...  41 

9.  Morphology  and  Eeproduction  of  Spongida,       .            .            .  .42 

10.  Paramozcium,    ........  46 

11.  Vaginicola,  Stentor,  and  Vorticella,         ...           .            .  .48 

12.  Diagram  of  Sea-anemone,       .            ..           ^           .            ...  51 

13.  Morphology  of  Hydrozoa,              ...           ...            .  .53 

14.  Tubularia  indivisa,      •       .   •            «,           .,           •            •            •  61 

15.  Morphology  of  Corynida,              »  .62 

16.  Eeproductive  Processes  of  Hydrozoa,,            »            ...  63 

17.  Morphology  of  Sertularida,          . .   ~     .  .           .            .            .  .67 

18.  Gonophore  of  one  of  the  Campanularida,     ....  68 

19.  DipJiyes  appendiculata,       .           .           .           .    ,       .            .  .71 

20.  Portuguese  Man-of-War  and  Velella^             ....  73 

21.  Naked-eyed  Medusao,        .           .           .            .           .            .  .75 

22.  Lucernaria  auricula,    .           .           .            .            .            .           .  78 

23.  Development  of  Lucernarida,       ...            .            .            .  .79 

24.  Generative  Zooid  of  one  of  the  Lucernarida,           ...  81 

25.  Transverse  Sections  of  Actinozoa  and  Hydrozoa,            .            .  .85 

26.  Morphology  of  Actinidce,        ......  86 

27.  Structure  of  Coral-reefs,    .......      89 

28.  Pennatula  phospfiorea,              ......  91 

29.  Morphology  of  Corals,       .            .            .            .            .            .  .92 

30.  Plewdbrachia  pileus,    .......  93 

31.  Morphology  of  EcJiinoidea,            .            .            *            .            .  .      97 

32.  Cidaris papillata,          .......  98 


x  LIST   OF   ILLUSTRATIONS. 

FIG.  FAGE 

33.  Cribella  oculata,      .            .            .            .            .            .            .  .    100 

34.  Morphology  of  OpMuroidea,  .            .            .            .                    .     .  102 

35.  Comatula  rosaeea,    .            .            .            .            .            .  .     103 

36.  Khizocrinus  Lofotensis,             ......  104 

37.  Cystidean,   .........     105 

38.  Holothurian,      ........  106 

39.  Morphology  of  Tceniada,               .           .•           .           .           .  .     109 

40.  Morphology  of  Trematoda,      .            .            .           .           .  112 

41.  Morphology  of  Turbellaria,          .           .            .                       .  .113 

42.  Free  Nematodes,          .           .            .           .           .           .           ,  115 

43.  Morphology  of  Botifera,    .           .           .           .           .            .  .116 

44.  Diagram  of  an  Annulose  Animal,      .           .           .           .           .  118 

45.  Syrinx  nudus,         .           .            .            .            .            .            .  .119 

46.  Section  of  an  Annelide,           .            .           .           .           .           .  120 

47.  Morphology  of  Hirudinea,             .            .        -   ;            .            .  .122 

48.  Morphology  of  Tubicola,         .           «           .           .           .           ...  123 

49.  Morphology  of  Errant  Annelides,            ,           .           ,           V  .     124 

50.  Lobster,                        «           . ..        .           .           .           ,           .  130 

51.  Spiny  Spider-crab,              .       "    .            ..          .            i    -     ;  *  •'  .132 

52.  Morphology  of  Isopoda,           .            .            ^           ,            .            .  133 

53.  King-crab,               .            .           .           .           .           .         . ..-  .     134 

54.  Pterygotus  Anglicw,     .            .            •            .            *            ,         ••'.  134 

55.  Morphology  of  Trilobites,             .           .           .           .           ,  .135 

56.  Fresh-water  Entomostraca,      .         .  .           ,           ..           »           f  136 

57.  Morphology  of  Cirripedia^            ..           .           .    ,        ..           .  .137 
57i.  Morphology  of  Podosomata  and  Acarina,     .            .            .            .  141 

58.  Scorpion,      .            .-           .            .                     -   .            .-           .  .142 

59.  Theridion  riparium,     .            .            .            .            .            ;            .  143 

60.  Scolopendra,            .            .            .            .            .           ...  .145 

61.  Millipede,         .• 145 

62.  External  Anatomy  of  Insect,        .            .           .        -  .        .   .  .     147 

63.  Digestive  Apparatus  of  Beetle,           .            .           .                       .  148 

64.  Metamorphosis  of  Magpie-moth,             .            .           ..           .  .     151 

65.  ApUsfdba:, 154 

66.  Cockroach,               .            .           .            .            ....  .     155 

67.  Migratory  Locust,         .            .            .            .            ...  156 

68.  Aphis-lion,              .            .            .            ...                  :   -.  .     157 

69.  Termes  bellicosus,    '.-..-          ..                       ....  157 

70.  Tipula  oleracea,       .           ,.•           .            .            .         '  -,    <   -•   ,-  .     158 

71.  Larva,  Pupa,  and  Imago  of  Cabbage-butterfly,        .            .            .  159 

72.  Gooseberry  Saw-fly,           „           .           «,           .                    •    .  .    161 

73.  Myrmica  rufa,              ,            .            .            .*           .            .            .  162 

74.  Cockchafer,             .           .-          .           .           .            .            .  .163 

75.  Diagram  of  a  Mollusk,            ..          .           «.          .           .        -  . .  164 

76.  Morphology  of  Polyzoa,     .            .            ..           «.          .            .  .     169 

77.  Flustra,  ValTceria,  and  LopTiopus,      .....  170 

78.  Morphology  of  Tunicata^  ......    172 


LIST  OF  ILLUSTRATIONS.  xj 

FIO.  PAGE 

79.  Lingitla  anatina,        .......  175 

80.  Anatomy  of  a  Bivalve  Mollusk,  .  .  .  .  .177 

81.  Shells  of  Lamellibranchiata,  .....  178 

82.  Ampullaria  canaliculata,  .  .  .  .  ,  .181 

83.  Tongue  of  Whelk, 182 

84.  Shells  of  Gasteropoda, 183 

85.  Doris  JoJimtoni,          .......  184 

86.  Carinaria  cymbium,          .  .  .  .  .  .  .184 

87.  Limax  Sowerbyi,         .  .  .  .  .  .  .  185 

88.  Morphology  of  Pteropoda,  .  .  .  .  .  .180 

89.  Sepiola  Atlantica,       .  .  .  .  .  .  .187 

90.  Paper  Nautilus,     .  .  .  .  .  .  .  .191 

91.  Pearly  Nautilus,         .  .  .  .  .  .  .193 

92.  Orthoceras,  .  .  .  .  .  .  .  .193 

93.  Diagram  of  Invertebrata,  and  Vertebrata,      ....  196 

94.  Lumbar  Vertebra  of  Whale,  and  Diagram  of  Thoracic  Vertebra,      .     198 

95.  Skeleton  of  Beaver,    .......  199 

96.  Fore-limb  of  Chimpanzee,  .  .  .  .  .  .200 

97.  Hind-limb  of  Chimpanzee,    ......  200 

98.  Digestive  System  of  a  Mammal,  .....     202 

99.  Blood-corpuscles  of  Vertebrata,         .....  203 

100.  Scales  of  Fishes,   ........     207 

101.  Skeleton  of  Perch,      .......  208 

102.  Outline  of  a  Fish, 209 

103.  Tails  of  Fishes,      '     .       ' 210 

104.  Diagram  of  the  Circulation  of  a  Fish,    .  .  .  .  .211 

105.  Diagram  of  the  Lancelot,      .  .  .  .  .  .  215 

106    Lamprey,  .  .  .  .  .  .  .217 

107.  Ganoid  Fishes,  :     .'          .  .  .  .  .  221 

108.  Cephalaspis  Lyellii,  .  .  .  .  .  .  .222 

109.  White  Shark  and  Chimcera,         ' 222 

110.  Lepidosiren  annectens,       .......     224 

111.  Siphonops  annulatus,  ......  227 

112.  Axolotl, •        .  .  .228 

113.  Great  Water-newt,     .......  229 

114.  Tree-frog,  .  .       '     * 230 

115.  Development  of  the  Common  Frog,  ....  231 

116.  Skull  of  a  Python, .     235 

117.  Diagram  of  the  Circulation  of  a  Reptile,     ....  237 

118.  Skeleton  of  a  Tortoise,    *  .  .  .  .  .  .     239 

119.  Hawk's-bill  Turtle,    .  240 

120.  Naja  Haje, .241 

121.  Eye  and  Head  of  Viper,        .  .  .  .  .  .  243 

122.  Slow-worm,  ........     246 

123.  Scincus  officinalis,       .......  247 

124.  Crocodilus  vulgaris,          .  .  .  .  .  .  .     248 

125.  Ichthyosaurus,  .......  249 


xii  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGE 

126.  Plesiosaurus,         .  .  .  .  .  .  .  .250 

127.  Pterodactyle, ;  .  251 

1'28.  Shoulder-girdle  and  Fore-limb  of  Penguin,      .  .  .  .     256 

129.  Hind-limb  of  the  Loon, 257 

130.  Digestive  System  of  the  Fowl, 259 

131.  Penguin,        .  .......  266 

132.  Common  Heron,   .  .  .  .  .  .  .  .268 

133.  Apteryx  Australia,      .  .  .  .  .  .  .270 

134.  Eock -pigeon,         ........     272 

135.  Purple-capped  Lory,  ......  274 

136.  Heads  and  Feet  of  Insessores,       ......     275 

137.  Foot  of  Peregrine  Falcon  and  Head  of  Buzzard,     .  .  .  277 

138.  Foot  and  Head  of  Owl,    .  .  .  .  •   .    •        .     278 

139.  ArcTioBopteryx  macrura,          .'          .  .  .-          .       :     .  -•        279 

140.  Lower  Jaw  of  Chimpanzee,  .  .  .  i  .     283 

141.  Diagram  of  the  Circulation  in  a  Mammal,  .  .  «    •       «  285 

142.  OrnithorTiynchus,  .  .  .  .  .  .  .289 

143.  Pkascolarctos  cinereus,  ,  ,  .  •          .  .  290 

144.  Chlamyphorus  truncatus,  .  .          • .  .  .  .292 

145.  Dugong,  .  .'  .  .  .         .  .  .          •.  294 

146.  DelpJiinus  del/phis,  .  .  >  .  .          '»  .     296 

147.  Feet  of  Ungulata,       .  .  .  .  .          \  .  297 

148.  Head  of  Two-horned  Khinoceros,  .  .  .  .  .     298 

149.  Stomach  of  Sheep,      .  .  .  .  .  .300 

150.  Head  of  Cervus  elapfius,    .  .  .  .  .  .302 

151.  Head  of  Strepsiceros  Koodoo,  .  .  .  »  .  303 

152.  Skull  of  Indian  Elephant,  .'  .-  .  .  .  .305 

153.  Feet  of  Carnivora,      .  .  .  .  .  .  .  306 

154.  Greenland  Seal,    .  .  .  .  .  .  .  .307 

155.  Skull  of  Beaver,          .  .  .  .  .          310 

156.  Hamster,   .  .  .  .  .  0  .310 

157.  Skeleton  of  a  Bat,    -  •.  .  .  .  .  .  312 

158.  European  Mole,    ........     314 

159.  Cercocebw  sabceus,       .......  317 

160.  Skulls  of  Orang  and  European  Adult,  .  .  .  .318 


ZOOLOGY. 


INTRODUCTION. 
1.   DEFINITION  OF  BIOLOGY  AND  ZOOLOGY. 

ALL  natural  objects  may  be  roughly  divided  into  three 
groups  constituting  the  so-called  Mineral,  Animal,  and  Vegeta- 
ble kingdoms.  The  objects  comprised  in  the  mineral  kingdom 
are  all  devoid  of  life,  and  they  exhibit  the  following  characters : 
a.  Their  chemical  composition  is  simple.  They  consist  of 
either  a  single  element,  as  is  the  case,  for  instance,  with  native 
gold ;  or,  if  combined,  they  are  almost  always  in  nature  in  the 
form  of  simple  compounds,  composed  of  no  more  than  two  or 
three  elements — as,  for  example,  common  salt,  limestone,  plas- 
ter of  Paris,  and  many  others,  b.  Mineral  bodies  are,  when 
unmixed,  composed  of  similar  particles,  which  have  no  definite 
relations  to  one  another,  or,  in  other  words,  they  are  homo- 
geneous, c.  The  form  of  mineral  bodies  is  either  altogether 
indefinite,  when  they  are  said  to  be  "  amorphous ; "  or,  if  they 
have  a  definite  shape,  they  are  crystalline,  in  which  case  they 
are  usually  bounded  by  plane  surfaces  and  straight  lines,  d. 
When  mineral  bodies  increase  in  size,  as  crystals  may  do,  the 
increase  is  produced  simply  by  the  addition  of  particles  from 
the  outside  (technically  called '"  accretion  ").  e.  Mineral  bodies 
exhibit  no  phenomena  which  are  not  purely  physical  and  chem- 
ical, and  they  show  no  tendency  to  periodic  changes  of  any 
kind. 

All  the  bodies  which  exhibit  these  characteristics  properly 
belong  to  the  mineral  kingdom,  and  fall  to  be  treated  of  by  the 
sciences  of  Geology,  Mineralogy,  Chemistry,  and  Physics.  It 


2  INTRODUCTION. 

should  be  borne  in  mind,  however,  that,  in  the  case  of  what  are 
called  "  fossils  "  or  "  petrifactions,"  we  have  mineral  bodies 
which  owe  their  existence  and  characters  to  living  beings 
which  existed  at  former  periods  in  the  history  of  the  earth. 
For  this  reason,  fossils,  though  composed  of  mineral  matter, 
can  hardly  be  said  properly  to  belong  to  the  mineral  kingdom. 
On  the  other  hand,  the  objects  which  belong  to  the  animal 
and  vegetable  kingdoms  differ  from  those  which  are  comprised 
in  the  mineral  kingdom  in  the  following  points :  a.  They  are 
composed  of  few  chemical  elements,  of  which  carbon,  hydro- 
gen, oxygen,  and  nitrogen,  are  the  most  important ;  and  these 
elements  are  combined  to  form  complex  organic  compounds, 
which  always  contain  a  large  proportion  of  water,  are  very  un- 
stable, and  are  prone  to  spontaneous  decomposition.  #.  They 
are  composed  of  diverse  or  heterogeneous  parts,  which  have 
usually  more  or  less  definite  relations  to  one  another.  These 
heterogeneous  but  related  parts  are  termed  "  organs,"  and  the 
objects  possessing  them  are  said  to  be  "  organized."  Some  of 
the  lowest  forms  of  animals  have  bodies  composed  of  so  uni- 
form a  substance  that  they  cannot  be  said  to  be  organized,  as 
they  exhibit  no  definite  organs.  This  exception,  however,  does 
not  affect  the  general  value  of  this  distinction,  c.  They  are 
always  more  or  less  definite  in  shape,  presenting  concave  and 
convex  surfaces,  and  being  bounded  by  curved  lines,  d.  When 
they  increase  in  size,  or  "  grow,"  they  do  so,  not  by  the  addi- 
tion of  particles  from  the  outside,  but  by  the  reception  of 
foreign  matter  into  their  interior  and  its  assimilation  there 
(technically  called  "intussusception").  e.  They  invariably 
pass  through  certain  periodic  changes  in  a  definite  and  dis- 
coverable order ;  these  changes  constituting  life.  They  are 
subject  to  the  same  physical  and  chemical  laws  as  those  which 
govern  dead  matter,  but  the  living  body  is  the  seat  of  some- 
thing in  virtue  of  which  it  can  override  the  physical  laws  which 
enslave  mere  dead  matter.  The  living  body,  so  long  as  it  is 
a  living  body,  is  the  seat  of  energy,  and  can  overcome  the 
primary  law  of  the  inertia  of  matter.  It  has  certain  relations 
with  the  outer  world  other  than  the  merely  passive  ones  of 
dead  matter.  However  humble  it  may  be,  and  even  if  it  be 
permanently  rooted  to  one  place,  some  part  or  other  of  every 
living  body  possesses  the  power  of  spontaneous  and  inde- 
pendent motion — a  power  possessed  by  nothing  that  is  dead. 
In  the  higher  animals  the  relations  of  the  living  body  to  dead 
nature  become  still  further  complicated,  and  their  mastery 
over  the  physical  forces  becomes  more  and  more  pronounced, 


INTRODUCTION.  3 

till  in  man,  whose  complex  organization  is  wielded  by  an  un- 
dying intelligence,  we  have  a  being  in  whose  hands  the  dead 
matter  of  the  universe  is  obedient  as  plastic  wax.  f.  If  our 
observation  be  continued  for  a  sufficient  length  of  time,  we 
always  discover  that  every  living  body  has  the  power,  by  more 
or  less  complex  process,  of  reproducing  its  like.  That  is  to 
say,  it  has  the  power,  directly  or  indirectly,  of  giving  origin 
to  minute  germs,  which  can  be  developed  under  proper  con- 
ditions into  the  likeness  of  the  parent,  g.  Lastly,  all  living 
beings  alike  appear  to  be  primitively  composed  of  a  substance 
which  is  more  or  less  closely  allied  to  albumen  or  white-of-egg, 
and  which  has  been  termed  "protoplasm."  Vital  phenomena 
can  apparently  be  manifested  by  no  other  form  of  matter,  and 
protoplasm  bears  to  life  the  same  relation  that  a  conductor 
does  to  the  electric  current.  It  is  the  necessary  vehicle  and 
medium  through  which  life  is  brought  into  relation  with  the 
outer  world.  It  does  not,  however,  follow  from  this,  as  has 
been  assumed,  that  protoplasmic  matter  holds  any  other  or 
higher  relation  to  life,  or  that  vital  phenomena  are  in  any 
way  an  inherent  property  of  the  matter  by  which  they  are 
manifested. 

All  the  objects,  then,  which  fulfil  these  conditions,  are  said 
to  be  alive ;  and  they  all  belong  either  to  the  animal  or  to  the 
vegetable  kingdom.*  The  study  of  living  objects  of  all  kinds, 
irrespective  of  which  kingdom  they  belong  to,  is  conveniently 
called  by  the  general  name  of  Biology  (Gr.  Mos,  life;  and 
logos,  discourse).  As  all  living  objects,  however,  may  be  re- 
ferred to  one  or  other  of  these  two  kingdoms,  so  Biology  may 
be  divided  into  the  two  sciences  of  Botany,  which  treats  of 
plants,  and  Zoology  (Gr.  zoon,  animal ;  logos,  discourse),  which 
treats  of  animals.  The  term  Natural  History,  again,  is  gen- 
erally understood  nowadays  as  being  equivalent  to  Zoology 
alone,  though  originally  it  was  applied  to  the  study  of  all 
natural  objects  indiscriminately. 

2.    DIFFERENCES  BETWEEN  ANIMALS  AND  PLANTS. 

It  now  becomes  necessary  to  inquire  into  the  differences 
which  subsist  between  animals  and  plants,  and  which  enable 
us  to  separate  the  kindred  sciences  of  Zoology  and  Botany.  It 
might  have  been  thought  that  nothing  could  be  easier  than  to 

4  *  As  will  be  mentioned  immediately,  it  has  been  proposed  to  form  an  intermediate  king- 
dom between  the  animal  and  vegetable  kingdoms  for  the  reception  of  organisms  which 
cannot  certainly  be  stated  to  be  either  plants  or  animals.  There  does  not  appear,  however, 
to  be  any  necessity  for  this  in  the  mean  while. 


4  INTRODUCTION. 

determine  the  animal  or  vegetable  nature  of  any  given  or- 
ganism ;  and  such,  indeed,  was  the  almost  universal  belief 
of  older  observers.  In  point  of  fact,  however,  no  hard-and-fast 
line  can  be  drawn,  in  the  present  state  of  our  knowledge,  be- 
tween the  animal  and  vegetable  kingdoms,  and  it  is  often  a 
matter  of  extreme  difficulty,  or  even  wholly  impossible,  to 
decide  positively  whether  we  are  dealing  with  an  animal  or  a 
plant.  So  deeply  has  this  difficulty  been  felt  of  late,  that  a 
most  able  zoologist — Dr.  Ernst  Haeckel — has  proposed  to 
form  an  intermediate  kingdom,  which  he  calls  the  Regnum 
Prolisticum,  and  in  which  he  proposes  to  place  all  organisms 
of  a  doubtful  character.  Even  such  a  cautious  observer  as 
Professor  Rolleston,  while  questioning  the  propriety  of  this 
step,  is  forced  to  come  to  the  conclusion  that  "  there  are  or- 
ganisms which  at  one  period  of  their  life  exhibit  an  aggregate 
of  phenomena  such  as  to  justify  us  in  speaking  of  them  as  ani- 
mals, while  at  another  they  appear  to  be  as  distinctly  vege- 
table." In  the  case  of  the  higher  members  of  the  two  king- 
doms there  is  no  difficulty  in  arriving  at  a  decision.  The 
higher  animals  are  readily  separated  from  the  higher  plants 
by  the  possession  of  a  distinct  nervous  system,  of  locomotive 
power  which  can  be  voluntarily  exercised,  and  of  an  internal 
cavity  fitted  for  the  reception  and  digestion  of  solid  food.  The 
higher  plants,  on  the  other  hand,  possess  no  nervous  system  or 
organs  of  sense,  are  incapable  of  voluntary  changes  of  place, 
and  are  not  provided  with  any  definite  internal  cavity,  their 
food  being  wholly  fluid  or  gaseous. 

The  lower  animals  (Protozoa)  cannot,  however,  be  separated  in  many 
cases  from  the  lower  plants  (Protophytd)  by  these  distinctions,  since  many 
of  the  former  have  no  digestive  cavity,  and  are  destitute  of  a  nervous  system, 
and  many  of  the  latter  possess  the  power  of  active  locomotion.  In  determin- 
ing, therefore,  the  nature  of  these  ambiguous  organisms,  the  following  are 
the  chief  points  to  be  attended  to : 

Firstly,  as  to  mere  form  or  external  configuration,  no  certain  rules  can 
be  laid  down  for  separating  animals  and  plants.  Many  of  the  lower  plants, 
either  in  their  earlier  stages  of  existence  or  when  grown  up,  are  exactly 
similar  in  form  to  some  of  the  lower  animals.  This  is  the  case,  for  ex- 
ample, in  some  of  the  Algce,  which  closely  resemble  some  of  the  Infusorian 
animalcules.  Many  undoubted  animals,  again,  are  rooted  to  solid  objects 
in  their  adult  state,  and  are  so  plant-like  in  appearance  as  to  be  always 
popularly  regarded  as  vegetables.  This  is  the  case  with  many  of  the 
so-called  hydroid  zoophytes,  such  as  the  sea-firs,  and  also  with  the  much 
more  highly  organized  sea-mats  (Flustrd),  all  of  which  are  usually  regarded 
as  sea-weeds  by  seaside  visitors.  This  is  also,  but  less  strikingly,  the  case 
with  the  corals  and  sea-anemones,  of  which  the  latter  are  often  spoken  of  as 
"  sea-flowers." 

Secondly,  no  decided  distinction  can  be  drawn  between  animals  and 


INTRODUCTION.  5 

plants  as  to  their  minute  internal  structure.  Both  alike  consist  essen- 
tially of  minute  solid  particles  (molecules  or  granules),  of  cells,  or  of 
fibres. 

Thirdly,  as  regards  chemical  composition,  there  are  some  decided,  though 
not  universal,  differences  between  plants  and  animals.  As  a  general  rule,  it 
may  be  stated  that  plants  exhibit  a  decided  predominance  of  what  are 
known  to  chemists  as  "  ternary  compounds  " — that  is  to  say,  compounds 
which,  like  sugar,  starch,  and  cellulose,  are  composed  of  the  three  elements, 
carbon,  hydrogen,  and  oxygen.  They  are,  comparatively  speaking,  poorly 
supplied  with  "  quaternary  "  compounds,  which  contain  the  fourth  element, 
nitrogen,  in  addition  to  the  three  first  mentioned  (e.  g.,  gluten  and  legumin). 
Animals,  on  the  other  hand,  are  rich  in  quaternary  nitrogenized  compounds, 
such  as  albumen  or  fibrine.  Still  in  both  kingdoms  we  find  nitrogenized 
and  non-nitrogenized  compounds,  and  it  is  only  in  the  proportion  which 
these  bear  to  one  another  in  the  organism  that  animals  differ  in  any  way 
from  plants.  The  most  characteristic  of  all  vegetable  compounds  is  the  one 
known  as  cellulose,  very  nearly  allied  in  its  chemical  composition  to  ordinary 
starch.  As  a  general  rule  it  may  be  stated  that  the  presence  of  an  external 
envelope  of  cellulose  in  any  organism  raises  a  strong  presumption  as  to  its 
vegetable  nature.  Still  cellulose  is  not  exclusively  confined  to  plants,  as 
was  at  one  time  believed.  It  is  now  well  known  that  the  outer  covering 
of  the  so-called  sea-squirts  or  Ascidian  Mollusks  contains  a  large  quantity 
of  cellulose  (as  much  as  60  per  cent,  in  some  cases) ;  and  recent  researches 
seem  to  prove  that  this  substance  is  present  also  in  some  of  the  lower  forms 
of  animal  life  (coccospheres).  Another  highly  characteristic  vegetable  prod- 
uct is  chlorophyll,  the  green  coloring-matter  of  plants.  Any  organism 
which  exhibits  chlorophyll  in  any  quantity  as  a  proper  element  of  its  tissues 
is  most  probably  vegetable.  In  this  case  also,  however,  the  presence  of 
chlorophyll  cannot  be  regarded  as  a  certain  test,  since  it  occurs  regularly  in 
some  undoubted  animals  (e.  g.,  Stentor  among  the  Infusoria,  and  the  Hydra 
viridis,  or  green  fresh-water  polype,  among  the  Cozlenterata). 

Fourthly,  as  regards  locomotive  power,  or  the  ability  to  effect  changes  of 
place  at  will,  the  results  of  observation  are  singularly  at  variance  with  our 
preconceived  notions.  Before  the  invention  of  the  microscope,  no  instances 
of  independent  voluntary  movements  were  known  in  plants,  if  we  except  the 
voluntary  opening  and  closure  of  flowers  and  their  turning  toward  the  sun, 
the  drooping  of  the  leaves  of  sensitive  plants  under  irritation,  and  some 
other  phenomena  of  a  like  nature.  Now,  however,  we  know  of  many  plants 
which  are  endowed,  either  when  young  or  throughout  life,  with  the  power 
of  effecting  voluntary  movements  apparently  as  spontaneous  and  independent 
as  those  exhibited  by  the  lower  animals.  In  some  cases  the  movements  are 
brought  about  by  means  of  little  vibrating  hairs  or  cilia  with  which  a  part 
or  the  whole  of  the  surface  is  furnished.  In  other  cases  the  movements 
seem  to  be  certainly  not  produced  by  cilia,  but  their  exact  cause  is  obscure 
(e.  g.,  in  the  Diatomacece  and  Desmidice,  two  of  the  lower  orders  of  plants,  all 
of  which  are  microscopic  in  size).  When  it  is  added  that  many  animals  are 
permanently  fixed  and  rooted  to  solid  objects  in  their  fully-grown  condition, 
it  will  be  seen  that  no  absolute  distinction  can  be  drawn  between  animals 
and  plants  merely  on  the  ground  of  the  presence  or  absence  of  independent 
locomotive  power. 

FiftJdy,  we  have  shortly  to  consider  one  of  the  most  reliable  of  all  the 
tests  by  which  an  animal  may  be  separated  from  a  plant — namely,  the  nature 
of  the  food,  and  the  products  which  are  formed  out  of  the  food  within  the 
body. 


6  INTRODUCTION. 

The  differences  between  animals  and  plants  in  this  respect  may  be  roughly 
stated  as  follows : 

1.  Plants  live  upon  purely  dead  or  inorganic  substances,  such  as  water, 
carbonic  acid,  and  ammonia — and  they  have  the  power  of  making  out  of 
these  true  organic  substances,  such  as  starch,  cellulose,  sugar,  etc.     Plants, 
therefore,  take  as  food  very  simple  bodies,   and   manufacture  them   into 
much  more  complex  substances,  so  that  plants  are  the  great  producers  in 
nature. 

2.  Plants  in  the  process  of  digestion  break  up  carbonic  acid  into  the  two 
elements  of  which  it  is  composed — namely,  carbon  and  oxygen,  keeping  the 
carbon  and  setting  free  the  oxygen.     As  carbonic  acid  occurs  always  in  the 
air  in  small  quantities,  the  result  of  this  is  that  plants  remove  carbonic  acid 
from  the  atmosphere  and  give  out  oxygen. 

3.  Animals,  on  the  other  hand,  have  no  power  of  living  on  dead  or  in- 
organic matters,  such  as  water,  carbonic  acid,  and  ammonia.     They  have  no 
power  of  converting  these  into   the   complex  organic  substances  "of  which 
their  bodies  are  composed.     On  the  contrary,  animals  require  to  be  supplied 
with  ready-made  organic  compounds  if  their  existence  is  to  be  maintained. 
These  they  can  only  get  in  the  first  place  from  plants,  and  therefore  ani- 
mals are  all  dependent  upon  'plants  for  food  either  directly  or  indirectly. 
Animals,  therefore,  differ  from  plants  in  requiring  as  food  complex  organic 
bodies  which  they  ultimately  reduce  to  very  much  simpler  inorganic  bodies. 
While  plants,  then,  are  the  great  manufacturers  in  nature,  animals  are  the 
great  consumers.     Another  distinction  arising  from  the  nature  of  their  food 
is,  that  while  plants  decompose  carbonic  acid,  keeping  the  carbon  and  setting 
free  the  oxygen,  animals  absorb  oxygen  and  give  out  carbonic  acid,  so  that 
their  reaction  upon  the  atmosphere  is  the  reverse  of  that  of  plants. 

As  regards  these  general  distinctions  between  plants  and  animals,  there 
are  three  points  which  should  be  remembered : 

1.  That,  even  if  universally  true,  these  distinctions  can  often  not  be  ap- 
plied in  practice  to  the  ambiguous  microscopic  organisms  about  which  alcne 
any  doubt  can  be  entertained. 

2.  These  general  laws  are  certainly  not  of  universal  application  in  the 
case  of  plants.     Some  fungi  are  known  which  in  the  matter  of  food  are  ani- 
mals— that  is  to  say,  they  cannot  live  upon  inorganic  materials  alone,  but 
require  ready-made  organic  products  for  their  support. 

3.  Recent  researches  have  rendered  it  not  unlikely  that  some  of  the 
lower  animals  have  the  power  of  acting  as  plants,  and  of  manufacturing 
organic  compounds  out  of  inorganic  materials. 

3.  CLASSIFICATION. 

By  the  term  classification  is  understood  the  arrangement 
of  a  number  of  dissimilar  objects  of  any  kind  into  larger  or 
smaller  groups  according  as  they  exhibit  more  or  less  likeness 
to  one  another.  The  number  of  different  animals  is  so  enor- 
mous that  it  was  long  ago  perceived  that  some  classification 
of  them,  or  method  of  arranging  them  into  groups,  was  abso- 
lutely indispensable.  Without  some  such  arrangement  it  would 
have  been  utterly  impossible  to  have  ever  acquired  a  clear 
notion  of  the  animal  kingdom  as  a  whole.  In  the  older 


INTRODUCTION.  7 

arrangements,  animals  were  grouped  in  accordance  with  some 
particular  character,  which  might  or  might  not  be  a  really 
essential  one ;  and  the  result  was  that  these  classifications 
were  "artificial,"  and  not  "natural,"  as  they  are  when  all  the 
characters  are  taken  into  consideration.  To  take  a  familiar 
example  of  this :  when  we  speak  of  "  quadrupeds,"  we  really 
do  so  in  consequence  of  our  having,  consciously  or  uncon- 
sciously, formed  something  like  a  rough  classification  of  the 
animal  kingdom.  We  have  a  dim  idea  that  all  animals  with 
four  legs  belong  together  somehow,  and  form  a  single  group. 
Our  classification,  however,  is  founded  upon  a  single  character 
only — the  possession,  namely,  of  four  legs ;  and  it  is,  there- 
fore, a  purely  artificial  arrangement.  It  will,  however,  be 
practically  good  or  bad,  just  as  this  single  character  expresses 
a  genuine  and  fundamental  distinction,  or  is  of  a  merely  trivial 
and  superficial  nature.  The  instance  here  chosen  will  serve  to 
illustrate  either  case.  If  we  insist  upon  the  fact  that  all  the 
four  legs  must  be  externally  visible,  unmistakable  legs,  never 
fewer  in  number  than  four,  then  our  classification  is  a  very  bad 
one,  in  fact  entirely  "  artificial."  In  this  case  our  group  of 
"quadrupeds"  will  comprise  only  the  ordinary  four-legged 
mammals,  such  as  oxen,  sheep,  horses,  and  such-like — together 
with  the  very  dissimilar  groups  of  the  four-legged  reptiles  and 
amphibians,  such  as  tortoises,  lizards,  crocodiles,  frogs,  and 
newts.  Now,  these  different  animals  have  certainly  much  in 
common,  but  we  are  not  justified  in  placing  them  together 
simply  upon  the  ground  that  they  have  four  conspicuous  legs, 
unless  we  are  willing  to  put  in  a  vast  number  of  other  animals 
as  well.  We  must,  in  fact,  put  in  a  great  number  of  animals 
which  are  not  quadrupeds  in  the  sense  that  they  have  four  legs, 
but  which  agree  with  those  that  have  four  legs  in  the  other 
fundamental  and  essential  points  of  their 'structure.  In  this 
way  we  may  arrive  at  a  very  genuine  and  natural  classification 
by  making  some  concessions.  We  must  allow,  for  instance, 
that  two  of  the  legs  or  limbs,  ceasing  to  be  fit  for  walking, 
may  be  converted  into  organs  of  flight,  or  wings.  This  will 
let  in  the  birds.  We  must  allow,  again,  that  all  the  limbs 
may  be  converted  into  fins.  This  admits  most  of  the  fishes. 
We  must  further  grant  that  two  of  the  legs  may  be  altogether 
absent  while  the  remaining  two  are  converted  into  swimming- 
paddles.  This  will  bring  in  the  whales  and  dolphins.  Lastly 
— and  this  is  the  greatest  admission  of  all — we  must  allow 
the  total  absence  of  all  the  limbs,  provided  the  animal  only 
show  those  other  essential  characters  which  are  invariably 


8  INTRODUCTION. 

found  to  go  along  with  the  possession  of  four  legs  in  the  regu- 
lar quadrupeds.  This  will  bring  in  the  snakes  and  some  of 
the  fishes.  So  that,  paradoxical  as  it  may  seem,  it  is  in  one 
sense  scientifically  correct  to  speak  of  a  snake  as  a  quadruped, 
though  in  reality  it  has  no  legs  at  all.  In  other  words,  there 
is  no  reason  why  a  snake  should  not  some  day  be  found  with 
four  legs,  and  in  point  of  fact  some  snakes  show  rudiments  of 
these  appendages.  Making  these  allowances,  and  some  more 
of  a  similar  nature,  we  may  ultimately  succeed  in  converting 
our  division  of  Quadrupeds  into  a  strictly  scientific  group, 
comprising  the  Mammals,  the  Birds,  the  Reptiles,  the  Amphi- 
bia, and  the  Fishes.  In  fact,  our  group  of  Quadrupeds  now 
agrees  exactly  with  the  great  and  natural  division  of  the  Ver- 
tebrata  or  vertebrate  animals.  It  is  true  that  all  vertebrate 
animals  have  not  got  four  limbs,  or  not  obviously  so,  but  they 
never  have  more  than  four  under  any  circumstances  ;  and  a 
closer  examination  soon  shows  us  that  they  agree  with  one 
another  in  many  other  characters  which  are  of  much  greater 
importance  than  the  characters  of  the  limbs  alone. 

We  have  arrived,  then,  at  the  grand  principle  of  all  good 
classification — namely,  that  we  should  group  together  those 
objects  only  which  are  united  by  essential  and  fundamental 
points  of  similarity,  and  that  in  so  doing  we  should  ignore  all 
mere  superficial  resemblances.  The  question  now  arises, 
What  are  these  essential  and  fundamental  points  in  the  case 
of  animals  ? 

If  for  the  moment  we  look  at  animals  simply  as  so  many 
machines,  we  shall  not  find  much  difficulty  in  answering  this 
question.  Let  us  suppose  ourselves  placed  in  a  gigantic 
workshop  full  of  an  immense  number  of  complicated  and  curi- 
ously-constructed machines  of  different  sorts,  and  asked  to  put 
them  in  order — to  put  those  of  one  kind  in  one  place,  and 
those  of  another  kind  in  a  different  place.  How  should  we 
proceed  to  act  ?  Supposing,  in  the  first  place,  that  all  the 
machines  were  at  a  stand-still,  all  that  could  be  done  would 
be  to  examine  carefully  the  external  form  and  internal  struct- 
ure of  each,  and  to  do  our  best  to  pick  out  some  peculiarity 
which  would  distinguish  some  from  all  the  others.  In  this 
way,  if  our  mechanical  knowledge  were  sufficiently  extensive, 
we  should  no  doubt  ultimately  succeed  in  classing  all  our  ma- 
chines into  something  like  a  rough  natural  arrangement.  We 
should,  for  instance,  have  those  made  on  the  principle  of  the 
lever  in  one  place,  those  on  the  principle  of  the  inclined  plane 
in  another,  and  those  on  the  principle  of  the  pulley  in  a  third. 


INTRODUCTION.  9 

Still  our  classification  would  most  certainly  be  imperfect,  and 
in  some  cases  altogether  incorrect.  In  some  instances  the 
parts  of  the  machine  would  be  so  complex  as  to  be  utterly  in- 
comprehensible, and  in  many  cases  our  ignorance  of  what 
each  was  intended  to  effect  would  be  an  insuperable  bar  to 
our  arriving  at  any  arrangement.  Suppose  now,  however, 
that  all  the  machines  were  suddenly  set  in  motion,  so  that  we 
could  see  not  only  the  manner  in  which  they  were  constructed 
and  the  materials  of  which  they  were  composed,  but  could 
also  see  what  they  could  do — could  see,  in  fact,  for  what  work 
each  is  intended.  The  task  of  arrangement  now  becomes  im- 
mensely easier.  Our  previous  classification,  founded  simply 
upon  the  structure  of  the  machines,  is  now  supplemented  and 
rectified  by  our  knowledge  of  what  each  is  able  to  effect. 
One  machine  is  found  performing  one  set  of  actions,  another  a 
different  set ;  and  in  this  way  not  only  is  our  classification 
rendered  much  easier,  but  we  now  get  an  insight  into  the 
meaning  and  nature  of  many  points  of  structure  which  were 
formerly  obscure. 

To  make  this  illustration  fully  meet  the  case  of  the  natu- 
ralist who  deals  with  living  beings  only,  we  have  simply  to 
suppose  that  the  machines  to  be  examined  are  reasonably  per- 
fect in  their  parts  and  fit  for  work,  and  that  our  imaginary 
workshop  is  supplied  with  a  reasonable  amount  of  light,  not 
very  brilliant,  perhaps,  and  striking  upon  some  objects  more 
sharply  than  on  others,  but  still  upon  the  whole  moderately 
steady  and  uniform.  Far  worse,  however,  is  the  case  of  the 
naturalist  who  has  to  deal  with  the  remains  of  extinct  gen- 
erations of  animals  and  plants,  whose  work  lies  among  those 
relics  of  a  by-gone  world  which  are  known  as  "  fossils "  or 
"  petrifactions  " — objects  in  many  cases  more  wonderful  and 
more  perplexing  and  more  beautiful  than  the  most  ornate  and 
elaborate  productions  of  human  skill.  In  his  case  the  work- 
shop is  a  vast  and  gloomy  vault  or  charnel-house,  with  no  in- 
ternal source  of  light,  and  but  fitfully  illuminated  by  uncer- 
tain gleams  from  the  world  without.  And  what  is  worse  than 
this,  his  machines  are  mutilated  and  defaced,  in  many  cases 
wanting  their  most  important  parts,  in  all  cases  destitute  of 
life  and  motion,  and  usually  very  unlike  any  thing  visible  at 
the  present  day.  Nevertheless  it  is  almost  incredible  with 
what  certainty  and  precision  a  mere  fragment  of  a  fossil,  a 
single  tooth  or  bone,  can  be  referred  by  a  skilled  wrorker  in 
this  field  of  science  to  its  proper  place  in  the  animal  kingdom 
— with  what  exactitude  the  missing  parts  can  be  restored — 


10  INTRODUCTION. 

and  what  splendid  generalizations  can  be  drawn  from  what  at 
first  sight  would  appear  to  be  the  most  fragmentary  evidence. 

This  imaginary  illustration  exactly  expresses  the  points 
which  are  to  be  regarded  as  essential  and  fundamental  in  clas- 
sifying and  arranging  animals.  We  have  to  look,  namely, 
firstly,  to  the  plan  upon  which  each  animal  is  constructed ; 
secondly,  to  the  manner  in  which  it  discharges  its  vital  func- 
tions. These  are  the  two  points  of  view  from  which  every 
organism  may  be  regarded — in  their  nature  quite  distinct,  and 
indeed  sometimes  apparently  opposite.  From  the  one  point 
of  view  we  have  to  look  solely  to  the  laws,  form,  and  arrange- 
ment of  the  structures  of  the  organism.  This  constitutes  what 
is  technically  called  "  Morphology,"  or  the  science  of  form 
(from  the  Greek  words,  morphe,  form  ;  and  logos,  a  discourse). 
From  the  second  point  of  view,  we  are  concerned  simply  with 
the  functions  discharged  by  the  different  parts  of  the  organ- 
ism, and  this  constitutes  what  is  known  as  "  Physiology."  It 
is  most  important  to  remember  that  there  are  no  other  points 
in  which  it  is  possible  for  one  animal  to  differ  from  another. 
If  two  animals  are  different,  they  must  differ  in  one  or  other 
or  in  both  of  these  points.  Either  they  differ  morphologically, 
in  being  constructed  upon  altogether  different  plans ;  or  they 
differ  physiologically,  in  performing  a  different  amount  of 
vital  work  in  a  different  manner,  and  with  different  instru- 
ments ;  or  they  differ  both  morphologically  and  physiologi- 
cally. Philosophical  classification,  therefore,  insomuch  as  it 
depends  entirely  upon  a  due  appreciation  of  what  are  the 
real  differences  between  different  animals,  is  nothing  more 
than  an  attempt  to  express  formally  the  facts  and  laws  of  Mor- 
phology and  Physiology. 

Examining  next  into  the  nature  and  extent  of  the  morpho- 
logical or  structural  differences  between  different  animals,  we 
find  that  these  are  much  less  and  much  fewer  than  might  have 
been  thought.  By  one  not  previously  acquainted  with  the 
subject,  it  might  readily  be  supposed  that  every  kind  of  ani- 
mal was  constructed  upon  a  type  or  plan  peculiar  to  itself  and 
not  shared  by  any  other.  We  should  certainly  suppose,  for 
example,  that  animals  so  different  as  a  lobster  and  a  butterfly 
were  built  upon  different  types  or  plans  of  structure.  When 
we  come,  however,  to  examine  the  question,  we  find  that  this 
is  not  the  case.  The  lobster  and  the  butterfly  are  constructed 
upon  the  same  structural  plan  or  morphological  type.  What 
is  still  more  remarkable,  we  find  that  all  known  animals,  in 
spite  of  their  immense  differences  in  external  appearance,  are 


INTRODUCTION.  H 

really  constructed  upon  no  more  than  some  half-dozen  primary 
plans  of  structure  or  morphological  types.  These  types  are 
all  different  from  one  another,  but  there  is  no  animal  yet 
known  to  us,  living  or  extinct,  which  cannot  be  referred  to 
one  or  other  of  these  six  plans.  These  plans,  then,  give  us  the 
primary  basis  for  a  classification  of  the  animal  kingdom — all 
the  animals  formed  upon  one  plan  being  grouped  together  so 
as  to  form  a  single  division.  The  animal  kingdom,  therefore, 
is  primarily  divided  into  six  great  sections  corresponding  to 
the  six  morphological  types,  and  these  sections  are  known  to 
naturalists  under  the  name  of  the  "  sub-kingdoms."  Each  of 
these  sub-kingdoms  has  its  special  name,  and  it  is  the  object 
of  the  present  work  to  describe  the  leading  characters  and 
more  important  examples  of  each. 

We  have  to  understand,  then,  that  all  the  animals  belong- 
ing to  each  sub-kingdom  agree  with  one  another  in  their  mor- 
phological type,  or,  in  other  words,  in  the  plan  upon  which 
they  are  constructed  ;  and  the  question  now  arises  how  they 
can  be  separated  from  each  other.  If  they  agree  morphologi- 
cally, there  is  only  one  other  way  in  which  they  can  differ, 
and  that  is  physiologically r,  in  the  manner  in  which  they  dis- 
charge their  vital  functions.  Consequently,  all  animals  which 
agree  with  one  another  in  their  plan  of  structure,  and  which 
are  therefore  placed  in  the  same  sub-kingdom,  are  separated 
from  one  another  solely  by  their  physiological  perfection.  In 
other  words,  as  machines,  they  are  constructed  of  the  same 
fundamental  parts,  but  they  do  their  work  in  a  different  way 
and  with  different  instruments. 

Returning  to  our  old  illustration,  suppose  we  had  sepa- 
rated from  the  mass  of  machines  before  us  all  those  which 
were  intended  to  mark  the  lapse  of  time,  and  had  in  this  way 
assembled  a  large  collection  of  hour-glasses,  watches,  time- 
pieces, and  clocks,  and  suppose  that  we  wanted  to  arrange 
these  more  minutely,  we  should  soon  discover  that  each  of 
these  different  time-keepers  was  formed  upon  a  principle  pe- 
culiar to  itself.  The  hour-glasses,  as  the  most  simple,  would 
form  one  division  ;  the  timepieces  and  clocks,  possessing  pen- 
dulums, would  form  another ;  and  the  watches  would  form  a 
third.  These,  as  being  constructed  upon  different  plans,  would 
constitute  three  distinct  groups,  which  we  should  call  classes 
or  sub-kingdoms  according  to  the  value  we  might  see  fit  to 
place  upon  the  differences  between  them.  But  we  must  fur- 
ther suppose  that  we  wished  to  divide  one  of  these  groups — 
say  the  watches — into  still  smaller  groups.  If  they  were  all 


12  INTRODUCTION. 

standing,  we  should  probably  find  this  a  matter  of  very  great 
difficulty.  The  moment,  however,  that  they  commenced  to 
go — or,  in  other  words,  to  perform  their  own  peculiar  func- 
tion— we  should  soon  see  that  some  would  be  different  to 
the  others.  Some,  for  instance,  would  strike  the  hours,  and 
these  would  have  to  be  laid  aside  in  a  group  by  themselves. 
And  we  should  further  discover  that,  in  accordance  with  the 
difference  in  the  function,  there  would  be  an  equivalent  dif- 
ference in  the  structure,  of  these  two  groups.  The  striking 
watches  would  be  formed  upon  the  same  fundamental  type  as 
those  which  did  not  strike  ;  but,  in  addition  to  the  broad  and 
general  details  of  structure  in  which  all  were  the  same,  the 
striking  watches  would  have  a  special  apparatus  or  structure 
fitted  for  striking  the  hours.  The  non-striking  watches  would 
be  destitute  of  this  apparatus,  so  that  the  physiological  or 
functional  difference  between  the  two  groups  would  thus  en- 
tail a  corresponding  difference  in  structure. 

It  is  just  the  same  with  animals.  Tf  we  take  a  lobster,  a 
butterfly,  a  scorpion,  and  a  spider,  we  find  that,  dissimilar  as 
they  are  in  external  appearance,  they  are  all  constructed  upon 
the  same  fundamental  plan.  They  agree  in  morphological 
type,  and  they  belong  to  the  same  sub-kingdom.  They  lead 
different  lives,  however — they  are  placed  under  different  con- 
ditions— and  they  discharge  different  functions  in  the  general 
economy  of  Nature.  They  differ,  therefore,  physiologically  ; 
and,  as  every  physiological  difference  implies  a  corresponding 
structural  difference,  they  differ  structurally  as  well.  But 
they  differ  structurally  only  because  they  differ  physiologi- 
cally, and  in  all  the  really  essential  details  of  their  structure 
they  are  the  same.  The  lobster  is  aquatic  in  its  habits,  and 
has  therefore  gills,  or  organs  adapted  for  breathing  air  dis- 
solved in  water.  The  butterfly  is  aerial,  and  has  respiratory 
organs  adapted  for  breathing  air  directly,  and  not  through  the 
medium  of  water.  They  differ,  then,  physiologically,  and 
therefore,  necessarily,  in  the  corresponding  structure.  Both, 
however,  have  distinct  organs  set  apart  and  dedicated  to  the 
function  of  respiration.  This  is  an  essential  and  fundamental 
point  in  their  structure,  and  in  this  they  both  agree  with  one 
another,  and  differ  from  a  large  number  of  animals  in  which 
there  are  no  distinct  breathing-organs.  It  is  only  by  the  com- 
bined effect  of  a  number  of  these  physiological  differences, 
taken  collectively,  that  the  lobster  and  the  butterfly  come  ulti- 
mately to  be  so  strikingly  distinct  from  one  another 

It  is  now  possible  to  comprehend  fully  the  principles  upon 


INTRODUCTION.  13 

which  a  naturalist  proceeds  in  framing  a  classification  of  the 
animal  kingdom.  His  great  primary  divisions  are  founded  up- 
on differences  in  the  smaller  and  fundamental  details  of  struct- 
ure. His  smaller  divisions  are  based  upon  the  less  important 
physiological  differences  with  their  corresponding  structural 
distinctions.  Of  course,  in  carrying  out  this  programme  of  a 
truly  philosophical  and  natural  classification,  the  naturalist 
works  to  a  great  extent  in  the  dark,  and  is  liable  to  many 
sources  of  error.  It  is  by  no  means  always  easy  to  deter- 
mine what  points  of  structure  are  essential  and  fundamental, 
and  what  are  only  caused  by  physiological  differences.  Such, 
too,  is  the  constitution  of  the  human  mind,  that  different  ob- 
servers place  different  values  upon  the  same  structures ;  points 
which  some  look  upon  as  of  essential  value  are  regarded  by 
others  as  of  a  merely  superficial  nature.  Nevertheless  there 
can  be  no  doubt  that  the  progress  of  Natural  History  as  a 
science  has  been  strictly  conterminous  with  the  development 
of  these  great  principles  of  classification. 

In  the  present  work  an  outline  is  given  of  the  morpho- 
logical differences  between  all  the  larger  groups  of  the  animal 
kingdom,  but  it  may  be  as  well  here  to  say  a  few  words  upon 
the  subject  of  Physiology.  As  already  remarked,  Physiology 
treats  of  all  the  functions  exercised  by  living  bodies,  or  dis- 
charged by  the  various  definite  parts  or  organs  of  which  most 
animals  are  composed.  All  these  various  functions  come  un- 
der three  great  heads  :  1.  Functions  of  Nutrition,  comprising 
all  those  functions  by  means  of  which  an  animal  is  able  to  live, 
grow,  and  maintain  its  existence  as  an  individual.  2.  Func- 
tions of  Reproduction,  comprising  all  the  functions  by  which 
fresh  individuals  are  produced  and  the  perpetuation  of  the 
species  insured.  3.  A  series  of  functions  which  are  known 
by  the  somewhat  misleading  name  of  the  Functions  of  Rela- 
tion or  of  Correlation.  Under  this  term  are  included  all  those 
functions  by  means  of  which  external  objects  are  brought  into 
relation  with  the  organism,  and  by  which  it,  in  turn,  reacts 
upon  the  outer  world.  The  functions  of  nutrition  and  repro- 
duction are  often  spoken  of  collectively  as  the  functions  of 
"  organic  "  or  u  vegetative  "  life,  as  being  common  to  animals 
and  plants  alike.  The  functions  of  relation,  again,  are  often 
called  the  functions  of  "  animal  "  life,  as  being  most  highly 
developed  in  animals.  These  functions,  however,  though  more 
highly  characteristic  of  animals,  are  not  peculiar  to  them,  bir'- 
are  manifested  to  a  greater  or  less  extent  by  various  plants. 

As  regards  animals,  all  alike,  whatever  their  structure  may 


14  INTRODUCTION. 

be,  perform  the  three  great  physiological  functions — that  is  to 
say,  they  all  nourish  themselves,  reproduce  their  like,  directly  or 
indirectly,  and  have  certain  relations  with  the  external  world. 
When  we  come,  however,  to  compare  animals  together  physio- 
logically, it  is  soon  seen  that  the  functions  of  relation  stand  in 
quite  a  different  position  to  that  occupied  by  the  functions  of 
nutrition  and  reproduction.  As  far  as  these  last  are  con- 
cerned, there  can  be  no  difference  in  the  amount  or  perfection 
of  the  function  discharged  by  the  organism.  The  simplest 
and  most  degraded  of  animals — say  a  sponge — nourishes  it- 
self as  perfectly,  as  far  as  the  result  to  itself  is  concerned,  as 
does  the  highest  of  animals.  Nutrition  can  do  no  more  than 
maintain  the  body  of  any  animal  in  a  healthy  and  vigorous 
condition.  This  is  the  highest  possible  perfection  of  the  func- 
tion, and  it  is  attained  as  fully  and  perfectly  by  the  sponge  as 
it  is  by  man  himself.  The  same  holds  good  of  reproduction. 
While  the  functions  of  nutrition  and  reproduction  are  thus,  as 
regards  their  essence  and  results,  the  same  in  all  animals,  it 
must  be  remembered  that  there  are  enormous  differences  in 
the  manner  in  which  the  functions  are  discharged.  The  result 
attained  is  in  all  cases  the  same,  but  it  may  be  arrived  at  in 
the  most  different  ways  and  with  the  most  different  apparatus. 
As  regards  the  functions  of  relation,  on  the  other  hand,  we 
have  every  possible  grade  of  perfection  exhibited  as  we  as- 
cend from  the  lowest  members  of  the  animal  kingdom  to  the 
highest.  So  numerous,  in  fact,  are  the  changes  in  these  func- 
tions, and  so  great  the  additions  which  are  made  in  the  higher 
organisms,  that  it  may  be  doubted  if  there  exists  any  common 
element  by  which  a  comparison  can  be  drawn  on  this  head  be- 
tween the  higher  and  lower  animals.  It  may  reasonably  be 
doubted  whether  in  this  respect  a  horse  or  a  dog  has  any 
thing  in  common  with  a  sponge. 

Instead  of  giving  here  a  general  sketch  of  each  of  the  great 
physiological  functions  as  a  whole,  it  may  be  as  well  to  accom- 
pany the  morphological  account  of  each  primary  division  of 
animals  with  a  short  account  of  the  manner  in  which  the  vital 
functions  are  carried  out  in  the  same.  In  this  way  a  clearer 
view  will  be  obtained  of  the  gradual  rise  in  physiological  per- 
fection in  passing  from  the  bottom  to  the  summit  of  the  ani- 
mal series. 

HOMOLOGY  AND  ANALOGY. — In  connection  with  the  mor- 
phological and  physiological  differences  between  animals,  a 
.  short  explanation  may  be  given  of  the  meaning  of  the  terms 
Homology  and  Analogy,  which  are  in  constant  use  in  zoologi- 


INTRODUCTION.  15 

cal  works.  When  organs  in  different  animals  agree  with  one 
another  in  their  plan  of  structure,  they  are  said  to  be  "  homolo- 
gous," no  matter  what  may  be  the  functions  which  they  perform. 
For  example,  the  arm  of  a  man,  the  fore-leg  of  a  horse,  the  wing 
of  a  bird,  and  the  swimming-paddle  of  a  dolphin  or  whale,  are 
all  composed  essentially  of  the  same  structural  elements,  and 
they  are  therefore  said  to  be  homologous,  though  they  are 
fitted  for  altogether  different  functions. 

On  the  other  hand,  when  organs  in  different  animals  per- 
form the  same  functions,  they  are  said  to  be  "  analogous," 
whatever  their  fundamental  structure  may  be.  Thus  the 
wing  of  a  bat,  the  wing  of  a  bird,  and  the  wing  of  an  insect, 
all  serve  for  flight,  and  they  are  therefore  "  analogous  "  organs. 
They  are  all,  however,  constructed  upon  different  plans,  and 
they  are,  therefore,  not  "homologous."  At  the  same  time, 
however,  it  is  to  be  remembered  that  there  are  plenty  of  cases 
in  which  organs  in  different  animals  are  not  only  constructed 
upon  the  same  plan,  but  also  perform  the  same  function,  so 
that  they  are  both  homologous  and  analogous. 

GENERAL  DIVISIONS  OF  THE  ANIMAL  KINGDOM. 

As  already  stated,  the  entire  animal  kingdom  may  be  di- 
vided into  some  half-dozen  primary  plans  of  structure  or  mor- 
phological types,  to  one  or  other  of  which  every  known  animal 
is  referable.  These  primary  types  are  known  to  naturalists  as 
the  sub-kingdoms,  under  the  following  names :  Protozoa,  Coe- 
lenterata,  Annuloida,  Annulosa,  Mollusca,  and  Vertebrata.  The 
characters  and  minor  subdivisions  of  these  sub-kingdoms  form 
the  subject  of  the  remainder  of  this  work.  In  the  mean  while, 
it  is  sufficient  to  state  that  Ihe  first  five  of  these  are  often 
grouped  together  under  the  collective  name  of  the  Inverte- 
brata,  or  "  invertebrate  animals."  The  Invertebrata,  compris- 
ing the  Protozoa,  Ccelenterata,  Annuloida,  Annulosa,  and 
Mollusca,  are  collectively  distinguished  by  the  following 
points  among  others :  The  body,  if  divided  transversely,  or 
cut  in  two,  shows  only  a  single  tube  containing  all  the  vital 
organs  (Fig.  1,  A).  These  organs,  in  the  higher  Invertebrata, 
consist  of  an  alimentary  or  digestive  cavity,  a  circulatory  or 
"  haemal "  system,  and  a  nervous  or  "  neural "  system.  The 
side  of  the  body  on  which  the  "  haemal "  or  blood-vasculai 
system  is  placed  is  called  the  "  haemal  aspect ; ''  while  the  side 
of  the  body  on  which  the  main  masses  of  the  nervous  system 
are  situated  is  called  the  "neural  aspect."  When  there  is 


16 


INTRODUCTION. 


any  skeleton,  this  is  external  (forming  an  "  exo-skeleton "), 
and  it  is  really  nothing  more  than  a  hardening  of  the  skin. 
The  limbs,  when  present,  are  turned  toward  the  neural  aspect 
of  the  body. 

In  the  Vertebrate,  on  the  other  hand,  the  body,  if  trans- 
versely divided,  exhibits  two  tubes.  In  one  (Fig.  1,  B)  is  placed 
the  main  mass  of  the  nervous  system  (the  brain  and  spinal 


FIG.  1. — Diagrams  representing  transverse  sections  of  one  of  the  higher  Invertebrata,  A — 
and  one  of  the  Vertebrata,  B.  a  Wall  of  the  body ;  b  Alimentary  canal ;  c  Haemal  or 
blood-vascular  system  ;  n  Nervous  system ;  n'  Cerebro-spinal  axis,  or  brain  and  spinal 
cord  of  the  Vertebrata,  enclosed  in  a  separate  tube :  ch  Noto-chord  or  chorda  dorsalis. 
(Slightly  altered  from  Huxley.) 

cord).  In  the  other  tube  are  the  alimentary  canal,  the  haemal 
or  blood-vascular  system,  and  certain  other  portions  of  the 
nervous  system,  which  are  known  as  the  "  sympathetic  "  sys- 
tem of  nerves,  and  which  correspond  to,  or  are  homologous 
with,  the  entire  nervous  system  of  the  Invertebrata.  Further, 
in  the  Vertebrata  there  is  always  an  internal  skeleton  (or 
endo-skeleton),  the  central  stem  of  which  is  usually  consti- 
tuted by  a  true  backbone  or  "  vertebral  column."  When  this  is 
not  present,  there  is  always  a  structure  which  will  be  after- 
ward described  as  the  "  noto-chord  "  or  "  chorda  dorsalis." 
Lastly,  the  limbs  of  the  Vertebrata^  when  present,  are  never 
more  than  four  in  number,  and  they  are  always  turned  away 
from  the  neural  aspect  of  the  body — away,  that  is,  from  the 
side  on  which  the  main  masses  of  the  nervous  system  are 
placed. 

Subjoined  is  a  short  tabular  view  of  the  main  existing 
divisions  of  the  Animal  Kingdom,  the  characters  and  smaller 
divisions  of  which  will  be  considered-  hereafter  at  length : 


INTRODUCTION.  17 

INVERTEBRATE    ANIMALS. 
SUB-KINGDOM  L— PROTOZOA. 

Animal  simple  or  forming  colonies,  usually  very  minute  ;  the  body  com- 
posed of  the  structureless,  jelly-like,  albuminous  substance  called  "sarcode;" 
not  divided  into  regular  segments  ;  having  no  nervous  system ;  no  regular 
circulatory  system ;  usually  no  mouth ;  no  definite  body-cavity,  or  at  most 
but  a  short  gullet. 

CLASS  A.  GREGARINID.E — Minute  Protozoa  which  inhabit  the  interior  of 
insects  and  other  animals,  and  which  have  not  the  power  of  throwing  out 
prolongations  of  their  substance  (pseudopodia).  No  mouth. 

CLASS  B.  RHIZOPODA  (Root-footed  Protozoa). — Protozoa  which  are 
simple  or  compound,  and  have  the  power  of  throwing  out  and  retracting  pro- 
longations of  the  body-substance  (the  so-called  "pseudopodia  "  ).  No  mouth, 
in  most,  if  not  hi  all. 

Order  1.     Monera. — Ex.     Protogenes. 

Order  2.     Amcebea.—Ex.     Proteus  Animalcule  (Amoeba). 

Order  3.     Foraminifera. — Ex.     Lagena,  Nodosaria,  Globigerina. 

Order  4.  *  Radiolaria. — Ex.     Thalassicolla,  Polycystina. 

Order  5.     Spongida. — Ex.     Fresh-water  Sponge  (Spongilla),  Venus's 

Flower-Basket  (Euplectella). 

CLASS  C.  INFUSORIA  (Infusorian  Animalcules). — Protozoa  with  a  mouth 
and  short  gullet ;  destitute  of  the  power  of  emitting  pseudopodia ;  furnished 
with  vibratile  cilia  or  contractile  filaments ;  the  body  usually  composed  of 
three  distinct  layers. 

Order  1.     Ciliata. — Ex.     Bell-animalcule  (Vorticella),  Paramcecium. 

Order  2.     Flagellaia. — Ex.     Peranema. 

Order  3.     Suctoria. — Ex.     Podophyra. 

SUB-KINGDOM  II.—C<ELENTERATA. 

Animals  whose  alimentary  canal  communicates  freely  with  the  general 
cavity  of  the  body  ;  body  composed  essentially  of  two  layers  or  membranes, 
an  outer  layer  or  "  ectoderm,"  and  an  inner  layer  or  u  endoderm."  No  cir- 
culatory system  or  heart,  and  in  most  no  nervous  system.  Skin  furnished 
with  minute  stinging  organs  or  "  thread-cells."  Distinct  reproductive  organs 
in  all. 

CLASS  A.  HYDROZOA. — Walls  of  the  digestive  sac  not  separated  from 
those  of  the  general  body-cavity,  the  two  coinciding  with  one  another.  Re- 
productive organs  external. 

Sub-class  I.     HYDROIDA  (Hydroid  Zoophytes). 

Order  1.     Hydroida. — Ex.     Fresh-water  Polype  (Hydra). 
Order  2.     Corynida. — Ex.     Pipe-coralline  (Tubularia). 
Order  3.     Sertularida.—Ex.     Sea-firs  (Sertularia). 
Sub-class  II.     SIPHONOPHORA  (Oceanic  Hydrozoa). 
Order  4.     CalycopJioridce. — Ex.     Diphyes. 

Order  5.     Physophoridce. — Ex.     Portuguese  Man-of-War  (Physalia). 
Sub-class  III.     DISCOPHORA  (Jelly-fish). 

Order  6.     Medusidce. — Ex.     Trachynema. 
Sub-class  IV.     LUCERNARIDA  (Sea-blubbers). 

Order  7.     Lucernariadce. — Ex.     Lucernaria. 

Order  8.     Pelagidce. — Ex.     Pelagia. 

Order  9.     Rhizostomidce. — Ex.     Rhizostoma. 


18 


INTRODUCTION. 


Sub-class  V.     GRAPTOLITID.E  (extinct). 

CLASS  B.  ACTINOZOA. — Stomach  opening  below  into  the  body-cavity, 
which  is  divided  into  a  number  of  compartments  by  a .  series  of  vertical 
partitions  or  "mesenteries."  Reproductive  organs  internal. 

Order  1.  Zoantharia. — Tentacles  simply  rounded,  in  multiples  of  five 
or  six. — Ex.  Sea-Anemones  (Actinidae),  Star-corals 
(Astraeidae),  Brain-corals  (Meandrina),  Madrepores  (Ma- 
dreporidae). 

Order  2.     Alcyonaria. — Tentacles  fringed,  in  multiples  of  four. — Ex. 
Dead-man's-toes  (Alcyonium),   Organ-pipe  Coral  (Tubi- 
pora),  Sea-rods  (Virgularia),  Sea-pens  (Pennatula),  Red 
Coral  (Corallium). 
Order  3.     Rugosa  (extinct). 

Order  4.  Ctenopkora. — Animal  oceanic,  swimming  by  means  of 
bands  of  cilia  or  "  ctenophores." — Ex.  Pleurobrachia, 
Venus's  Girdle  (Cestum). 

SUB-KINGDOM  III.—ANNULOIDA. 

Animals  in  which  the  alimentary  canal  is  completely  shut  off  from  the 
general  cavity  of  the  body,  and  in  which  there  is  a  distinct  nervous  system. 
A  true  blood-circulatory  system  may  or  may  not  be  present.  In  all  there  is 
a  peculiar  system  of  canals,  which  usually  communicate  with  the  exterior, 
and  which  constitute  what  is  called  the  "  water-vascular  system."  The  body 
of  the  adult  is  never  composed  of  a  succession  of  definite  rings,  or  provided 
with  successive  pairs  of  appendages  disposed  symmetrically  on  the  two  sides 
of  the  body. 

The  Annuloida  are  divided  into  two  great  classes : 

A.  ECHINODERMATA. — Integument  composed  of  numerous  calcareous  plates 
jointed  together,  or  leathery  and  having  grains,  spines,  or  tubercles  of  cal- 
careous matter  developed  in  it.     Water-vascular  system  (ambulacral  system) 
mostly  employed  in  locomotion,  and  generally  communicating  with  the  ex- 
terior.    Adult  generally  more  or  less  starlike  or  "  radiate  "  in  shape ;  young 
mostly  showing  more  or  less  complete  "  bilateral  symmetry,"  that  is,  show- 
ing similar  parts  on  the  two  sides  of  the  body.     Nervous  system  radiate. 

Order  1.  Crinoidea. — (Sea-lilies).  —  Ex.  Feather-star  (Comatula). 
Medusa-head  Crinoid  (Pentacrinus),  Stone-lily  (Encri- 
nus.) 

Order  2.     Blastoidea  (extinct). 

Order  3.     Cysloidea  (extinct). 

Order  4.  Ophiuroidea  (Brittle-stars). — Ex.  Sand-stars  (Ophiura), 
Brittle-stars  (Ophiocoma). 

Order  5.  Asteroidea  (Star-fishes).— jEz.  Cross-fish  (Uraster),  Sun- 
star  (Solaster),  Cushion-star  (Goniaster). 

Order  6.  Ecliinoidea  (Sea-urchins). — Ex.  Sea-eggs  (Echinus),  Heart- 
urchins  (Spatangus). 

Order  7.  Holothuroidea  (Sea-cucumbers).  —  Ex.  Trepangs  (Holo- 
thuria).  • 

B.  SCOLECIDA. — Body  usually  flattened,  or  cylindrical  and  worm-like  ;  in- 
tegument soft,  without  lime.     Water-vascular  system  not  assisting  in  loco- 
motion.    Nervous  system  consisting  of  one  or  two  ganglia  or  little  masses, 
and  not  disposed  in  a  radiate  manner. 

Order  1.     Tceniada. — Ex.     Tape-worm  (Toenia). 

Order  2.     Trematoda  (Suctorial  worms). — Ex.     Liver-fluke  (Distoma). 


INTRODUCTION. 


19 


Order  3.     Turbellaria. — Ex.      Planarians   (Planaria),  Ribbon-worms 

(Nemertes). 
Order  4.     Acanthocephala    (Thorn-headed      worms). — Ex.      Echino- 

rhyncbus. 

Order  5.     Gordiacea  (Hair-worms). — Ex.     Gordius. 
Order  6.     Nematoda  (Thread-worms). — Ex.     Round-worm   (Ascaris), 

Guinea-worm  (Filaria),  Vinegar-eel  (Anguillula). 
Order  7.     JRotifera    (Wheel-animalcules). — Ex.       Builder-animalcule 

(Melicerta),  Flexible  Creeper  (Notommata). 


Order  2. 

Order  3. 
Order  4. 


SUB-KINGDOM  JV.—AyNULOSA. 

Animal  composed  of  numerous  definite  segments  or  "  somites,1'  arranged 
longitudinally,  one  behind  the  other.  Nervous  system  always  present,  con- 
sisting of  a  double  chain  of  nervous  masses,  or  ganglia,  which  are  placed  along 
the  lower  surface  of  the  body,  and  form  a  collar  around  the  gullet.  Limbs 
(when  present)  turned  toward  that  side  of  the  body  on  which  the  main 
masses  of  the  nervous  system  are  situated. 

DIVISION  A.  ANARTHROPODA.  —  Locomotive  appendages,  when  present, 
not  distinctly  jointed  or  articulated  to  the  body. 

CLASS  I.     GEPHYREA.  —  Ex.     Spoon-worms  (Sipunculus). 
CLASS  II.     ANNELIDA  (Ringed-worms). 

Order  1.     Hlrudinea.  —  Ex.     Leeches  (Sanguisuga,  Hirudo). 

Oliqochceta.  —  Ex.    Earth-worms  (Lumbricus),  Water-worms 

(Nais). 

Tubicola.  —  Ex.     Tube-worms  (Serpula). 
Errantia.  —  Ex.     Sand-worms  and  Sea-centipedes  (Nereis), 

Lob-worm  (Arenicola),  Sea-mouse  (Aphrodite). 
CLASS  III.     CHJBTOGNATHA  (Arrow-worms).  —  Ex.     Sagitta. 
DIVISION  B.     ARTHROPOUA.  —  Locomotive  appendages  jointed  or  articu- 
lated to  the  body. 

CLASS  I.  CRUSTACEA.  —  Respiration  aquatic,  mostly  by  gills.  Two  pairs 
of  antennae.  Limbs  more  than  four  pairs  in  number,  carried  upon  the  tho- 
rax, and  generally  the  abdomen  also. 

""  Order     1.     Rhizocephala.  —  Ex.     Peltogaster. 
Ichthyophthira.  —  Ex.     Leruaea. 
Cirripedia.  —  Ex.     Barnacles  (Lepas),  Acorn-shells  (Bala- 

nus). 

Ostracoda.  —  Ex. 
Copepoda.  —  Ex. 
Cladocera.—Ex. 

nia). 

Phyllopoda.—Ex. 
Trilobita  (extinct). 

Merostomata.  —  Ex.     King-crabs  (Limulus). 
Lcemodipoda.  —  Ex.     Whale-louse  (Cyamus). 
Isopoda.—Ex.     Wood-lice  (Oniscus),  Slaters  (Ligia). 
Amphipoda.  —  Ex.     Sandhopper  (Talitrus),   Fresh  -water 

Shrimp  (Gammarus). 

Stomapoda.  —  Ex.     Locust-shrimp  (Squilla). 
JDecapoda.  —  Ex.     Lobster  (Homarus),  Cray-fish  (Astacus), 
Shrimps  (Crangon)  ;    Hermit-crabs  (Pagurus);    Crabs 
(Cancer,  Careinus),  Land-crabs  (Gecarcinus). 
ARACHNIDA.  —  Respiration  aerial,  by  pulmonary  chambers  or 


Order 
Order 

Order 
Order 
Order 


—  Order     7. 
Order     8. 
Order     9. 

—  Order  10. 
Order  11. 

..-—   Order  12. 

-  Order  13. 
Order  14. 


CLASS  II. 


Water-fleas  (Cypris). 
Cyclops. 
Branched-horned  Water-fleas 

Brine-shrimp  (Artemia). 


(Daph- 


20 


INTRODUCTION. 


air-tubes  (tracheae)  in  the  higher  forms.  Antennae  converted  into  jaws. 
Head  and  thorax  amalgamated.  Four  pairs  of  legs.  Abdomen  without 
limbs. 

Order  1.     Podosomata  (Sea-spiders). — Ex.     Pycnogonum. 
,         p  Order  tf    Monomerosomata. — Ex.     Mites  (Acarus),  Water-mites  (Hy- 

drachna),  Ticks  (Ixodes). 
Order  B.     Adelarthrosomata.  —  Ex.      Harvest-spiders    (Phalangidae), 

Book-scorpions  (Chelifer). 

3  Order  ,4.,    Pedipalpi. — Ex.     Scorpions  (Scorpio). 
fr   Order  Jb.    Araneida. — Ex.     House-spiders  (Tegenaria),  Field-spiders 

(Epeira). 

CLASS  III.  MYRIAPODA. — Respiration  aerial,  by  tracheae  (air-tubes)  or  by 
the  skin.  Head  distinct ;  remainder  of  body  composed  of  nearly  similar 
segments ;  legs  more  than  eight  pairs  in  number,  and  borne  partly  upon  the 
abdomen.  One  pair  of  antennae. 

Order  1.     Chilopoda. — Ex.     Centipedes  (Scolopendra). 
Order  2.     Chilognatha.—Ex.     Millipedes  (lulus). 
Order  3.     Pauropoda. — Ex.     Pauropus. 

CLASS  IV.  INSECTA. — Respiration  aerial,  by  tracheae.  Head,  thorax,  and 
abdomen  distinct.  One  pair  of  antennae.  Three  pairs  of  legs,  and  gen- 
erally two  pairs  of  wings  on  the  thorax.  No  locomotive  limbs  on  the 
abdomen. 

Order     1.     Anoplura. — Ex.     Lice  (Pediculus). 

Order     2.     Mallophaga  (Bird-lice). 

Order     3.     Thymnura  (Sp ringtails.) 

Order    4.     Hemiptera. — Ex.     Plant-lice  (Aphides),  Field-bug  (Penta- 

toma),  Cochineal  Insects  (Coccus). 
Order    6.     Ortlwpttra.  —  Ex.      Locusts   (Acrydium),  Grass-hoppers 

(Gryllus),  Crickets  (Achetina),  Cockroach  (Blatta). 
Order     6.     Neuroptera. — Ex.      White  Ants    (Termes),   Dragon-flies 

(Libellulidae),  May-flies  (Ephemeridee). 
Order     7.     Aphaniptera.—Ex.     Fleas  (Pulex). 

Order     8.     Diptera. — Ex.     Gnats  (Culex),  Crane-flies  (Tipula),  House- 
flies  and  Flesh-flies  (Musca). 
Order     9.     Lepidoptera  (Butterflies  and  Moths). 
Order  10.     Hymenoptera. — Ex.     Bees  (Apidae),  Humble-bees  (Bom- 
bidae),  Wasps  (Vespidae),  Ants  (Formicidae),  Saw-flies 
(Tenthredinidae). 

Order  11.     Slrepsiptera.—Ex.     Stylops. 
•     Order  12.     Coleoptera  (Beetles). 

SUB-KINGDOM  V.—MOLLUSCA. 

Animal  soft-bodied,  generally  with  a  hard  covering  or  shell.  Nervous 
system  consisting  of  a  single  ganglion  or  of  scattered  pairs  of  ganglia.  A 
distinct  heart  and  breathing-organ,  or  neither. 

The  Mollusca  may  be  divided  into  the  two  following  primary  divisions ; 
containing  the  following  classes : 

A.  MOLLUSCOIDA. — Nervous  system  consisting  of  a  single  ganglion  or  of 
a  principal  pair  of  ganglia.  No  heart,  or  an  imperfect  one. 

CLASS  I.  POLYZOA. — Animal  always  forming  compound  growths  or  colo- 
nies. No  heart.  The  mouth  of  each  zooid  surrounded  by 
a  circle  or  crescent  of  ciliated  tentacles.  —  Ex.  Sea-mats 
(Flustra),  Lace-coral  (Fenestella). 


INTRODUCTION.  21 

CLASS  II.  TUNICATA. — Animal  simple  or  compound,  enclosed  in  a  leathery 
or  gristly  case.  An  imperfect  heart. — Ex.  Sea-squirts 
(Ascidia). 

CLASS  III.  BRACHIOPODA. — Animal  always  simple ;  the  body  enclosed  in 
a  bivalve  shell.  Mouth  furnished  with  two  long  fringed 
processes  or  "  arms." — Ex.  Lamp-shells  (Terebratula). 

B.  MOLLUSCA  PROPER. — Nervous  system  consisting  of  three  principal 
pairs  of  ganglia.  Heart  well  developed,  consisting  of  at  least  two  chambers. 

CLASS  IV.  LAMELLIBRANCHIATA  (Bivalve  Shell-fish) : — No  distinct  head  ; 
no  teeth.  Body  enclosed  in  a  shell  which  is  "  bivalve,"  or 
composed  of  two  distinct  pieces.  One  or  two  leaf-like  gills 
on  each  side  of  the  body. — Ex.  Oyster  (Ostrea),  Scallop 
(Pecten),  Mussel  (Mytilus). 

CLASS  V.  GASTEROPODA. — A  distinct  head  and  toothed  tongue.  Shell 
absent  in  some,  but  mostly  present,  and  consisting  of  a  single 
piece  ("  univalve  ").  Locomotion  effected  by  creeping  about 
on  the  flattened  under  surface  of  the  body  ("  foot "),  or  by 
swimming  by  means  of  a  fin-like  modification  of  the  same. — 
Ex.  Whelks  (Buccinum),  Limpets  (Patella),  Sea-lemons 
(Doris),  Land-snails  (Helix),  Slugs  (Limax). 

CLASS  YI.  PTEROPODA. — Animal  oceanic,  swimming  by  means  of  two 
wing-like  appendages,  one  on  each  side  of  the  head.  Size 
minute. — Ex.  Cleodora. 

CLASS  YII.  CEPHALOPODA. — Animal  with  eight  or  more  arms,  placed  in  a 
circle  round  the  mouth.  Mouth  armed  with  jaws,  and  a 
toothed  tongue.  Two  or  four  plume-like  gills.  In  front  of 
the  body,  a  muscular  tube  ("  funnel ")  through  which  is  ex- 
pelled the  water  which  has  been  used  in  respiration.  An 
external  shell  in  some,  an  internal  skeleton  in  others. — Ex. 
Calamaries  (Loligo),  Cuttle-fishes  or  Poulpes  (Octopus), 
Paper-Nautilus  (Argonauta),  Pearly  Nautilus  (Nautilus). 


VERTEBRATE    ANIMALS. 
SUB-KINGDOM  VI—  VER  TEBRA  TA. 

Body  composed  of  a  number  of  definite  segments  arranged  longitudinally 
or  one  behind  the  other.  The  main  masses  of  the  nesvous  system  are  placed 
on  the  dorsal  aspect  of  the  body,  and  are  completely  shut  off  from  the  gen- 
eral body-cavity.  The  limbs  (when  present)  are  turned  away  from  that  side 
of  the  body  on  which  the  main  nervous  masses  are  situated,  and  are  never 
more  than  four  in  number.  In  most  cases,  a  backbone,  or  "vertebral 
column,"  is  present  in  the  fully-grown  animal. 

CLASS  I.  PISCES  (Fishes). — Breathing-organs  in  the  form  of  gills ;  heart 
usually  of  two  chambers,  rarely  of  three ;  blood  cold  ;  limbs,  when  present, 
converted  into  fins. 

Order  1.     Pharynyobranchii. — Ex.     Lancelet  (Amphioxus). 

Order  2.     Marsipobranchii. — Ex.      Lamprey  (Petromyzon),    Hag-fish 

(Myxine). 

Order  3.  Teleostd  (Bony  Fishes).— .Ex.  Eels  (Muraenidae),  Herrings 
(Clupeidaa),  Salmon  and  Trout  (Salmonidae),  Cod  and 
Haddock  (Gadidas),  Flat-fishes  (Pleuronectidae),  Perch 
(Percidae),  Mackerel  (Scomberidae). 


22 


INTRODUCTION. 


Order  4.     Ganoidei. — Ex.     Bony  Pike  (Lepidosteus),   Faddle  -  fish 

(Spatularia),  Sturgeon  (Sturio). 

Order  5.  Elasmobranchii. — Ex.  Sharks  (Carcharidae),  Dog-fishes 
(Scylliadae),  Saw -fishes  (Pristis),  Rays  and  Skates 
(Randse). 

Order  6.     Dipnoi. — Ex.     Mud-fish  (Lepidosiren). 

CLASS  II.    AMPHIBIA  (Amphibians). — Breathing-organs  in  the  young  in 
the  form  of  gills  alone,  afterward  lungs,  either  alone  or  associated  with  gills. 
Skull  jointed  to  the  backbone  by  two  articulating  surfaces  ("condyles"). 
Limbs  never  converted  into  fins.     Heart  in  the   young  of  two  chambers 
only,  in  the  adult  of  three  chambers.     Blood  cold. 
Order  1.     Labyrinlhodontia  (extinct). 
Order  2.     Ophiomorpha. — Ex.     Csecilia. 

OrderS.  Urodela  (Tailed  Amphibians).— Ex.  Water-newts  (Triton), 
Salamanders  (Salamandra),  Axolotl  (Siredon),  Mud-eel 
(Siren). 

Order  4.  Anoura  (Tailless  Amphibians). — Ex.  Frogs  (Rana),  Tree- 
frogs  ('Hyla),  Toads  (Bufo),  Surinam  Toads  (Pipa). 

CLASS  III.  REPTILIA  (Reptiles). — Respiratory  organs  in  the  form  of  lungs, 
never  in  the  form  of  gills.  Heart  three-chambered,  rarely  four-chambered, 
the  pulmonary  and  systemic  circulations  always  connected  together  directly, 
either  in  the  heart  itself  or  in  its  immediate  neighborhood.  Blood  cold. 
Skull  jointed  to  the  backbone  by  a  single  articulating  surface  or  "  condyle." 
Each  half  of  the  lower  jaw  composed  of  several  pieces.  Appendages  of  the 
skin  in  the  form  of  scales  or  plates. 

Order  1.  Chelonia. — Ex.  Turtles  (Cheloniid)ae,  Soft  Tortoises  (Trio- 
nycidae),  Terrapins  (Emydidse),  Land  Tortoises  (Tes- 
tudinidae). 

Order  2.     Ophidia. — Ex.     Vipers   (Viperidae),  Rattlesnakes  (Crota- 
lidae),   Sea-snakes   (Hydrophidae),   Boas    and    Pythons 
(Boidae). 
Order  3.     Lacertilia. — Ex.     Lizards  (Lacerta),  Iguanas   (Iguanidae), 

Monitors  (Varanidae),  Chameleons  (Chameleontidae). 
Order  4.     Crocodilia. — Ex.     Crocodiles,  Alligators,  Gavials. 
Order  5.     Ichthyopterygia  (extinct). — Ex.     Ichthyosaurus. 
Order  6.     Sauropterygia  (extinct). — Ex.     Plesiosaurus. 
Order  7.     Pterosauria  (extinct). — Ex.     Pterodactylus. 
Order  8.     Anomodontia  (extinct). — Ex.     Dicynodon. 
Order  9.     Deinosauria  (extinct). — Ex.     Iguanodon. 
CLASS  IV.     AVES  (Birds). — Respiratory  organs  in  the  form  of  lungs,  never 
in  the  form  of  gills.     Lungs  connected  with  air-receptacles  placed  in  different 
parts  of  the  body.     Heart  four-chambered.     Blood  warm.     Skull  connected 
with  the  backbone  by  a  single  articulating  surface  or  "  condyle."     Each 
half  of  the  lower  jaw  composed  of  several  pieces.     Appendages  of  the  skin 
in  the  form  of  feathers.     Cavities  of  the  chest  and  abdomen  not  separated 
by  a  complete   partition   (diaphragm).     Fore-limbs   converted   into  wings. 
Animal  oviparous. 

Order  1.  Natatores  (Swimmers). — Ex.  Penguins  (Spheniscidas),  Gulls 
(Laridas),  Ducks  (Anatidas),  Geese  (Ansermae),  Flamin- 
gos (Phaenicopteridae). 

Order  2.  Grattatores  (Waders).— ,5*.  Rails  (Rallidao),  Water-hens 
(Gallinulae),  Cranes  (Gruidse),  Herons  (Ardeidae),  Storks 
(Ciconinas),  Snipes  and  Woodcock  (Scolopacidae),  Plovers, 
Oyster-catchers,  and  Turnstones  (Charadriidae). 


INTRODUCTION. 


23 


Order  3.  Cursores  (Runners). — Ex.  Ostrich  (Struthio),  American 
Ostrich  (Rhea),  Emeu  (Dromaius),  Cassowary  (Casu- 
arius),  Apteryx. 

Order  4.  Rasores  (Scratchers). — Ex.  Grouse,  Ptarmigan,  Partridges, 
Pheasants,  Turkey,  Guinea-fowl,  Domestic  Fowl,  Pea- 
fowl (Gallinacei) ;  Doves,  Pigeons,  Ground-pigeons  (Co- 
lumbacei). 

Order  6.  Scansores  (Climbers). — Ex.  Cuckoos  (Cuculidae),  Wood- 
peckers (Picidse),  Parrots,  Cockatoos,  Parrakeets 
(Psittacidae),  Toucans  (Rhamphastidae),  Trogons  (Tro- 
gonidae). 

Order  6.  Insessores  (Perchers). — Ex.  Crows,  Magpies,  and  Jays 
(Corvidae),  Starlings  (Sturnidae),  Finches,  Grosbeaks, 
Larks  (Fringillidae),  Thrushes,  Blackbirds,  Orioles 
(Merulidae),  Creepers  and  Wrens  (Certhidae),  Humming- 
birds (Trochilidae),  Swallows  and  Martens  (HiruDdinidae), 
Swifts  (Cypselidae),  King-fishers  (Alcedinidae). 

Order  7.  Raptores  (Birds  of  Prey).— .Ex.  Owls  (Strigidae),  Falcons 
and  Hawks  (Falconidae),  Eagles  (Aquilina),  Vultures 
(Vulturidae). 

Order  8.  Saururce  (extinct). — Ex.  Archaeopteryx. 
CLASS  V.  MAMMALIA  (Mammals  or  Quadrupeds). — Respiratory  organs 
in  the  form  of  lungs,  which  are  never  connected  with  air-sacs  placed  in 
different  parts  of  the  body.  Heart  four-chambered.  Blood  warm.  Skull 
united  to  the  backbone  by  two  articulating  surfaces  or  "  condyles."  Each 
half  of  the  lower  jaw  composed  of  a  single  piece.  Appendages  of  the  skin 
iu  the  form  of  hairs.  Young  nourished  by  means  of  a  special  fluid — the 
milk — secreted  by  special  glands — the  mammary  glands.  Animal  vivipa- 
rous. 

A.  NON-PLACENTAL  MAMMALS. — The  young  not  provided  with  a  placenta. 
Order     1.     Monotremata. — Ex.     Duck-mole  (Ornithorhynchus),  Spiny 

Ant-eater  (Echidna). 

Order  2.  Marsupialia. — Ex.  Kangaroos  (Macropodidae),  Kangaroo- 
bear  (Phascolarctos),  Phalangers  (Phalangistida),  Opos- 
sums (Didelphidae),  Tasmanian  Devil  (Dasyurus). 

B.  PLACENTAL  MAMMALS. — The  young  provided  with  a  placenta. 

Order  3.  Edentata.  —  Sloths  (Bradypodidae),  Armadillos  (Dasy- 
podidae),  Hairy  Ant-eaters  (Myrmecophagidae),  Scaly 
Ant-eaters  (Manis). 

Order    4.     Sirenia. — Ex.     Manatee  (Manatus),  Dugong  (Halicore). 

Order  5.  Cetacea. — Ex.  Whalebone  -  whales  (Balaenidae),  Sperm- 
whales  (Physeteridae),  Dolphins  and  Porpoises  (Del- 
phinidae). 

Order  6.  Ungulata  (Hoofed  Quadrupeds). — Ex.  Rhinoceros ;  Tapir ; 
Horse,  Ass,  and  Zebra  (Equidae) ;  Hippopotamus ;  Hogs, 
and  Peccaries  (Suida) ;  Camels  and  Llamas  (Camelidae) ; 
Giraffe ;  Stags,  Elk,  Rein-deer  (Cervidae) ;  Antelopes 
( Antilopidae) ;  Sheep  and  Goats  (Ovidae);  Oxen  and 
Buffaloes  (Bovidae). 

Order     7.     Hyracoidea. — Ex.     Hyrax. 

Order    8.     Proboscidea. — Ex.     Elephants  (Elephas). 

Order  9.  Carnivora. —  Ex.  Seals  (Phocidae),  Bears  (Ursidae), 
Raccoons  (Procyon),  Badgers  (Melidae),  Weasels  and 
Otters  (Mustelida9),  Civets  and  Genettes  (Viverridae), 


24 


INTRODUCTION. 


Dogs,  Wolves,  and  Foxes  (Canidae) ;  Hyaenas  (Hyaeni- 
dae),  Cats,  Lynxes,  Leopards,  Tigers,  Lions  (Felidae). 

Order  10.  Rodentia. — Ex.  Hares  and  Rabbits  (Leporidae),  Porcu- 
pines (Hystricidae),  Beavers  (Castoridae),  Mice  and 
Rats  (Muridae),  Dormice  (Myoxidae),  Squirrels  and 
Marmots  (Sciuridae). 

Order  11.  Cheiroptera. — Ex.  Common  Bats  (Yespertilionidae), 
Horseshoe  Bats  (Rhinolophidae),  Vampire  bats  (Phyl- 
lostomidee),  Fox-bats  (Pteropidae). 

Order  12.  Insectivora. — Ex.  Moles  (Talpidae),  Shrew-mice  (Soricidae), 
Hedgehogs  (Erinaceidae). 

Order  13.  Quadrumana. — Ex.  Aye-aye  (Cheiromys),  Lemurs  (Le- 
muridaD),  Spider-monkeys  (Ateles),  Howlers  (Mycetes), 
Macaques  (Macacus),  Baboons  (Cynocephalus),  Gib- 
bons (Hylobates),  Orang  (Simia),  Gorilla  and  Chim- 
panzee (Troglodytes). 

Order  14.     Bimana. — Man  (Homo  Sapiens). 


INVERTEBRATE  ANIMALS, 


SUB-KINGDOM  L— PROTOZOA. 
CHAPTER  I. 

i.  GENERAL  CHARACTERS  OF  THE  PROTOZOA.     2.  CLASSIFICA- 
TION.    3.  GREGARINID^E. 

THE  sub-kingdom  Protozoa  (Gr.  protos,  first ;  and  zodn, 
an  animal),  as  the  name  implies,  is  the  lowest  division  of  the 
animal  kingdom,  and  its  limits  are  therefore  necessarily  not 
yet  strictly  defined.  The  Protozoa  comprise  an  enormous 
number  of  animals,  almost  all  of  which  are  so  small  as  to  be 
invisible  to  the  naked  eye,  and  can  only  be  satisfactorily  ex- 
amined under  pretty  high  powers  of  the  microscope.  For 
this  reason,  and  because  they  are  almost  universally  found  in 
water,  these  creatures,  often  popularly  called  "  animalcules," 
are  almost  unknown  to  the  majority  of  people.  Some  few, 
however,  attain  a  large  size,  and  of  these  the  sponges  are 
familiar  examples.  The  microscopical  forms  of  the  Protozoa 
swarm  in  most  stagnant  pools,  and  in  all  waters  charged  with 
organic  matter  so  as  to  afford  them  food.  Every  worker  with 
the  microscope  is  familiarly  acquainted  with  them,  and  they 
exhibit  phenomena  which  in  many  cases  render  them  objects 
of  the  highest  interest.  From  their  low  position  in  the  ani- 
mal scale,  it  arises  that  the  Protozoa  are  mainly  characterized 
by  the  absence  of  organs  and  structures  which  occur  in  higher 
beings,  and  they  possess  few  positive  characters  by  which  they 
can  be  distinguished. 

The  Protozoa  may  be  defined  as  animals,  generally  of 
very  minute  size,  composed  of  a  nearly  structureless,  jelly-like 


26  INVERTEBRATE  ANIMALS. 

substance  (catted  "sarcode"},  showing  no  composition  out  of 
distinct  segments,  having  no  distinct  internal  cavity,  no  ner- 
vous system,  and  either  no  organs  devoted  to  digestion,  or  at 
best  a  very  rudimentary  alimentary  apparatus. 

Of  all  the  points  enumerated  in  this  definition  as  charac- 
teristic of  the  Protozoa,  none  is  more  important  than  the  na- 
ture of  the  body-substance.  The  body  in  all  known  Protozoa 
is  composed  of  a  substance  which  is  generally  known  by  the 
name  of  "  protoplasm  " — or,  better,  "  sarcode  "  (Gr.  sarx,  flesh ; 
eidos,  form).  This  sarcode  is  a  gelatinous  substance,  very  like 
white-of-egg  to  look  at.  and  really  of  nearly  the  same  chemical 
constitution,  consisting  mainly  of  albumen,  or  of  some  body 
allied  to  albumen.  Generally,  however,  it  contains  numerous 
oil-globules  scattered  through  it.  The  sarcode  shows  the  phys- 
iological property  of  "  contractility  " — that  is  to  say,  under 
appropriate  stimuli,  or  at  the  will  of  the  animal,  it  may  be 
made  to  contract  or  shorten  its  dimensions,  thus  giving  rise 
to  movements.  As  a  rule,  no  other  structures  appear  in  the 
sarcode  except  minute  rounded  particles,  or  granules  and 
molecules,  but  in  some  cases  larger  definite  structures  are 
formed  out  of  it.  Of  this  nature  is  the  so-called  "  nucleus  " 
found  in  many  Protozoa. 

As  regards  their  internal  structure,  some  Protozoa  exhibit 
nothing  worthy  of  the  name  of  structure  at  all,  the  entire 
body  being  simply  composed  of  sarcode,  containing  scattered 
granules  (for  example,  the  Foraminifera).  In  other  cases 
there  are  found  certain  definite  bodies  which  are  known  as  the 
"  nucleus "  and  "  nucleolus,"  and  which  are  usually,  if  not 
always,  connected  with  reproduction.  Very  often,  too,  there 
are  found  certain  minute  cavities  or  chambers  which  close  and 
expand  at  definite  intervals,  and  which  are  known  as  the 
"  contractile  vesicles."  These  are,  doubtless,  rudimentary  or- 
gans of  circulation.  In  one  division  of  the  Protozoa  (the  In- 
fusoria) there  is  a  permanent  mouth  and  a  short  gullet,  but 
in  all  the  others  there  are  no  definite  organs  connected  with 
the  process  of  digestion.  In  no  Protozoon,  however,  without 
exception,  have  any  traces  of  a  nervous  system  been  hitherto 
detected ;  and  in  none,  even  in  those  which  possess  a  mouth, 
is  there  any  distinct  and  definite  cavity  or  chamber  within  the 
body  in  which  the  particles  of  food  are  received.  No  organs 
of  sense  exist  in  any  of  the  Protozoa — that  is  to  say,  there 
are  no  distinct  organs  fitted  for  the  reception  of  impressions 
produced  by  light  or  sound ;  but  the  general  surface  of  the 
body  appears  capable  of  receiving  the  impressions  produced 


PROTOZOA.  27 

by  contact  with  foreign  bodies,  and  therefore  acts  as  an  or- 
gan of  touch.  The  power  of  active  locomotion  is  enjoyed  by 
most  of  Protozoa  ;  but  in  some  cases  this  is  very  limited,  and 
in  other  cases  the  animal  is  permanently  fixed  (as  in  the 
sponges).  The  apparatus  of  locomotion  in  the  Protozoa  is  of 
a  varied  nature.  In  many  cases,  especially  in  the  higher 
forms,  movements  are  effected  by  means  of  little  hair-like  pro- 
cesses, which  are  called  "  cilia "  (Lat.  cilium,  an  eyelash), 
and  which  have  the  power  of  vibrating  or  lashing  to  and  fro 
with  great  rapidity.  In  other  cases  the  cilia  are  accompanied 
or  replaced  by  one  or  more  long  whip-like  bristles,  which  act 
in  the  same  fashion,  and  are  known  as  "  flagella."  Among 
the  lower  Protozoa  the  most  characteristic  organs  of  locomo- 
tion are  the  so-called  "  pseudopodia  "  (Gr.  pseudos,  falsity  ; 
podes,  feet).  These  consist  of  variously-shaped  filaments, 
threads,  or  finger-like  processes  of  sarcode,  which  the  animal 
can  thrust  out  from  any  or  every  part  of  its  body.  They  are 
not,  however,  definite  and  permanent  organs  like  the  cilia,  for 
they  can  be  produced  at  will,  and  when  they  are  again  with- 
drawn they  simply  melt  into  the  sarcode  of  the  body,  and 
leave  no  traces  of  their  existence. 

As  regards  the  classification  of  the  Protozoa,  a  rough  and 
useful  division  is  into  mouth-bearing  or  "  stomatode  "  Proto- 
zoa^ in  which  there  is  a  distinct  mouth ;  and  mouthless  or 
"astomatous"  Protozoa,  in  which  there  is  no  mouth.  It  is 
somewhat  doubtful,  however,  if  the  mouth-bearing  forms 
(namely,  the  Infusoria)  can  properly  be  kept  in  the  Protozoa, 
so  that  this  arrangement  is  not  a  very  good  one.  More  scien- 
tifically, the  Protozoa  are  divided  into  three  great  divisions  or 
"  classes,"  known  by  the  names  Gregarinidce,  Rhizopoda  and 
Infusoria,  all  of  which  require  special  examination. 

CLASS  I.  GKEGARIOTD^E. — The  Gregarinidce  may  be  de- 
fined as  parasitic  Protozoa  which  have  no  mouth,  and  have  no 
power  of  giving  out  pseudopodia.  They  are  usually  looked 
upon  as  forming  the  lowest  class  of  the  Protozoa  /  but  in  all 
probability  much  of  their  degraded  character,  as  we  shall  see 
in  other  cases,  is  due  to  the  fact  that  they  are  internal  para- 
sites, and  are  therefore  not  dependent  on  their  own  exertions 
for  food.  They  vary  in  size  from  less  than  the  head  of  a  small 
pin  up  to  nearly  half  an  inch  in  length,  when  they  look  some- 
thing like  small  worms  ;  and  they  are  found  inhabiting  the  in- 
testines of  various  animals,  especially  the  cockroach  and  the 
earthworm. 


28 


INVERTEBRATE  ANIMALS. 


In  anatomical  structure  a  Gregarina  usually  presents  the 
appearance  of  a  single  cell,  consisting  of  an  ill-defined  mem- 
branous envelope,  filled  with  a  more  or  less  granular  sarcode 
containing  fatty  granules,  and  having  in  it  a  little  central 
bladder  or  vesicle — the  "  nucleus  " — which  in  turn  encloses  a 
solid  particle  or  "  riucleolus  "  (Fig.  2,  a).  The  outer  covering 


FIG.  2. — Anatomy  and  reproduction  of  the  Gregarina  of  the  earthworm  (after  Lieberkiihn). 
a  Adult  Gregarina ;  b  The  same  "  encysted ; "  c  With  the  contents  broken  up  into 
pseudonavicelloe ;  d  Free  pseudonayicellae;  e  Contents  of  the  pseudonavicellse  when  lib- 
erated. 

or  cuticle  with  which  the  protoplasmic  body  is  enclosed  may 
be  quite  smooth,  or  it  may  be  furnished  with  bristles  or 
spines,  and  in  some  cases  even  cilia  have  been  observed.  Be- 
yond the  nucleus  and  nucleolus  (which  are  probably  connected 
with  reproduction),  no  definite  organs  have  been  detected  in 
the  Gregarince  ;  and  all  the  processes  of  assimilating  food 
and  getting  rid  of  waste  or  injurious  products  must  be  effected 
by  the  general  surface  of  the  body.  As  we  shall  see,  how- 
ever, this  is  common  in  internal  parasites,  which  are  not 
necessitated  to  live  upon  solid  food,  but  which  are  enabled  to 
subsist  simply  by  imbibing  the  nutritive  juices  of  their  hosts. 

The  following  is  a  brief  outline  of  the  process  of  reproduction  as  it  has 
been  observed  in  the  Gregarince,  sometimes  in  a  single  individual,  some- 
times in  two  individuals  which  have  come  together  and  completely  coalesced 
and  melted  into  one  another.  The  Gregarina  becomes  completely  motion- 
less, assumes  a  globular  form,  and  develops  round  itself  a  thick  structureless 
coat  or  envelope,  when  it  is  said  to  be  "  encysted  "  (Fig.  2,  b).  The  nucleus 
then  disappears,  and  the  sarcode  of  the  body  breaks  up  into  little  masses, 
which  are  at  first  rounded,  but  afterward  become  pointed  at  both  ends,  when 
they  are  called  "  pseudonavicellae  "  (Fig.  2,  c).  The  cyst  then  breaks  and 
the  pseudonaviceliae  escape,  when  they  give  origin  to  little  masses  of  sar- 
code, which  have  the  power  of  active  movement  and  of  throwing  out  pseudo- 
podia,  thus  coming  closely  to  resemble  the  animalcule  which  will  be  directly 
described  as  the  Amceba  (Fig.  2,  e}.  These  little  amoeba-like  masses,  if  they 
find  a  suitable  locality,  are  finally  developed  into  new  Grcgarince. 


CHAPTER  II. 
RHIZOPODA. 

THE  next  class  of  the  Protozoa  which  we  have  to  consider 
comprises  the  most  characteristic  and  typical  forms  of  the 
whole  sub-kingdom.  The  name  of  Rhizopoda,  or  "  root- 
footed  "  animalcules  (from  the  Greek,  rhiza,  root ;  and  podes, 
feet),  is  derived  from  the  fact  that  they  all  possess  the  power 
of  throwing  out  at  will  from  various  parts  of  the  body  the 
processes  of  sarcode  which  have  been  already  spoken  of  as 
pseudopodia,  and  by  which  they  both  move  and  obtain  food. 
In  fact,  the  Rhizopoda  may  be  shortly  defined  as  Protozoa 
which  have  no  mouth  and  possess  the  power  of  giving  out 
pseudopodia.  The  pseudopodia  vary  a  good  deal  in  shape 
and  in  other  characters  in  different  orders  of  the  Rhizopoda, 
but  they  have  invariably  the  character  of  being  nothing  more 
than  temporary  threads  or  finger-like  processes  of  sarcode, 
which  can  be  thrust  out  at  will,  and  which  melt  again  into  the 
substance  of  the  body  when  they  are  withdrawn. 

Five  distinct  types  of  structure  are  known  in  the  Rhizo- 
poda, and  these  constitute  as  many  distinct  orders,  which  are 
known  by  the  names  of  the  Monera,  Amoebea,  Foraminifera, 
Radiolaria,  and  Spongida. 

ORDER  I.  MONERA. — This  name  has  been  proposed  for  a 
small  group  of  organisms  which  merely  require  to  be  men- 
tioned. They  are  all  microscopic  in  size,  and  inhabit  the  sea. 
Their  sarcode-body  is  entirely  structureless  and  devoid  of  defi- 
nite organs  of  any  kind.  They  have  the  power,  however,  of 
throwing  out  innumerable  processes  of  the  body-substance  or 
"  pseudopodia,"  and  these  agree  in  their  characters  with  those 
which  will  be  afterward  described  as  characterizing  the  Fora- 
minifera.  They  are,  namely,  very  long  and  delicate  filaments 
of  sarcode,  which  unite  in  various  directions  so  as  to  form  a 
net-work,  in  which  the  particles  of  food  are  entangled.  The 
body  is  completely  naked,  and  the  Monera  differ  from  the 


30 


INVERTEBRATE  ANIMALS. 


Foraminifera,  chiefly  if  not  entirely,  in  this  absence  of  any 
hard  covering  or  shell. 

ORDER  II.  AMCEBEA. — This  order  is  characterized  by  the 
fact  that  the  pseudopodia  are  mostly  blunt  and  finger-like  in 
shape,  and  that  the  sarcode  of  the  body  contains  the  structures 
known  as  the  "  nucleus "  and  "  contractile  vesicle" 

As  the  type  of  the  order  may  be  taken  the  Amoeba  or  Pro- 
teus-animalcule, so  called  because  of  the  incessant  and  illimit- 
able changes  of  form  which  it  exhibits  (Gr.  amoibos,  chan- 
ging). The  Amoeba  is  a  little  microscopical  creature  which 
may  commonly  be  detected  in  stagnant  water,  especially 
where  there  is  decaying  vegetable  matter.  When  examined 
under  the  microscope,  all  that  would  probably  be  seen  at  first 
would  be  a  shapeless  or  irregularly- spherical  mass  of  gelati- 
nous, jelly-like  sarcode,  containing  scattered  granules.  Soon 
the  creature  might  be  observed  to  push  out  a  finger-shaped 
prolongation  of  its  own  substance  ;  and  it  would  soon  be 
found  that  similar  processes  or  pseudopodia  could  be  pushed 
out  at  will  from  almost  any  point  of  the  body  and  again  re- 
tracted within  it  without  leaving  any  trace  behind.  As  a 
result  of  this,  the  form  of  the  animal  is  constantly  changing, 
and  hence  its  common  name  of  Proteus-animalcule  (Fig.  3,  a). 
By  means  of  these  temporary  processes  of  sarcode,  the  Amoeba 


FIG.  3. — Morphology  of  Ehizopoda.  a  Amoeba  radiosa,  showing  the  pseudopodia,  the 
contractile  vesicle,  nucleus,  and  vacuoles  ;  b  Diffluqia,  with  the  pseudopodia  protruded 
from  the  anterior  end  of  the  carapace ;  c  Detached  sponge-particles  or  "  sarcoids ; " 
d  Ciliated  sponge-particles  of  Grantia;  e  Sponge-particle  of  the  fresh-water  sponge 
(Spongilla)  with  a  single  cilium. 

both  moves  and  obtains  foodl  Locomotion  is  effected  in  a 
kind  of  creeping  manner,  the  animal  pushing  out  the  pseu- 
dopodia in  one  direction  and  then  pulling  the  body  in  the 
same  direction.  In  the  same  way,  when  any  minute  particle 
of  food,  such  as  a  microscopic  plant,  comes  within  its  reach, 
the  Amoeba  wraps  a  pseudopodium  round  it,  and  then  with- 
drawing the  pseudopodium,  lodges  the  nutrient  particle  se 


RHIZOPODA.  31 

curely  in  the  substance  of  the  body.  It  follows  from  this  that 
the  Amoeba  has  no  permanent  mouth — no  aperture,  that  is, 
which  is  especially  employed  in  the  admission  of  food.  Any 
part  of  the  surface  can  be  pushed  out  into  a  pseudopodium, 
and  therefore  any  part  of  the  surface  can  be  extemporized 
into  a  mouth.  The  process  of  taking  food,  in  fact,  in  the 
Amoeba,  has  been  aptly  compared  to  thrusting  a  stone  or  any 
other  solid  body  into  a  lump  of  dough.  The  central  portion 
of  the  body  of  the  animal  is  softer  and  more  fluid  than  the 
outer  layers,  and  the  particles  of  food,  on  reaching  this  point, 
undergo  a  sort  of  digestion,  and  are  subjected  to  a  species  of 
movement  or  rotation  in  the  interior  of  the  animal.  Each 
particle  of  food,  in  the  process  of  being  taken  into  the  body, 
usually  carries  with  it  a  little  drop  of  water ;  and  in  this  way 
a  number  of  clear  spaces  are  formed,  which  are  usually  quite 
round,  and  look  like  distinct  cavities.  These  spaces  are  called 
"  vacuoles ; "  but  they  are  not  distinct  organs  of  any  kind, 
though  formerly  regarded  as  distinct  stomachs.  Having  un- 
dergone digestion,  any  portions  of  food  which  may  be  indigest- 
ible or  insoluble  are  simply  thrust  out  again  through  the  walls 
of  the  body.  This  appears  to  be  effected  at  one  particular 
part  of  the  body  ;  but  there  is  no  permanent  aperture  for  the 
purpose.  There  are  no  distinct  vessels  which  serve  to  convey 
the  nutritive  fluid  derived  from  the  digestion ;  but  there  does 
appear  to  be  a  rudimentary  organ  by  which  this  fluid  is  driven 
through  the  body.  If  we  watch  an  Amoeba  carefully,  there  is 
usually  no  difficulty  in  observing  that  every  now  and  again 
there  appears  at  one  particular  place  a  clear  spot,  "  like  a 
window,"  which  slowly  expands  to  its  full  extent,  and  then 
usually  contracts  slowly  till  it  disappears  altogether.  This 
process  of  gradual  expansion  and  contraction  is  what  is  called 
"  rhythmical " — that  is  to  say,  it  is  repeated  at  tolerably  regu- 
lar intervals,  perhaps  twice  a  minute.  In  some  cases  the 
vesicle,  when  contracted,  remains  so  for  a  long  time,  but  it 
always  reappears  in  the  same  place.  It  is  known  as  the  con- 
tractile vesicle ;  and  there  can  be  little  doubt  that  it  is  a 
permanent  organ.  It  is,  in  fact,  a  little  clear  space  or  cavity 
in  the  substance  of  the  body,  filled  probably  with  the  nutri- 
tive fluid  derived  from  the  digestion,  and  no  doubt  serving  by 
its  contraction  to  drive  this  fluid  to  various  parts  of  the  body. 
In  its  function,  then,  the  contractile  vesicle  of  the  Amoeba  is 
to  be  looked  upon  as  the  first  indication  which  we  have  in  the 
entire  animal  kingdom  of  that  most  important  organ,  the 
heart. 


32  INVERTEBRATE  ANIMALS. 

The  Amoeba  possesses  no  breathing-organs,  of  any  kind, 
and  no  excretory  organs,  so  that  these  functions  must  be  per- 
formed by  the  general  surface  of  the  body  in  a  manner  some- 
what the  same  as  the  exhalation  from  the  skin  which  takes 
place  in  the  higher  animals.  There  are  also  no  traces  of  a  ner- 
vous system,  and  no  organs  of  sense,  and  the  only  other  struct- 
ure of  any  kind  is  what  is  known  as  the  nucleus.  The  nucleus 
is  simply  a  small  rounded  or  oval  granular  mass,  and  there  may 
be  more  than  one  in  the  same  individual.  Its  function,  how- 
ever, is  quite  unknown,  though  it  is  probably  connected  with 
reproduction.  The  means  employed  by  the  Amoeba  to  per- 
petuate the  species  are  various,  but  the  only  one  which  need 
be  mentioned  is  the  process  by  self-division.  This  is  what  is 
technically  called  "  fission  "  (Lat  findo,  I  cleave),  and  it  con- 
sists in  a  gradual  division  or  cleavage  of  the  body  into  two 
parts,  each  of  which  then  becomes  a  separate  and  independent 
individual.  In  some  cases  this  process  is  slightly  varied,  a 
single  pseudopodium  alone  being  cast  off  and  becoming  a 
fresh  Amoeba,  but  this  does  not  differ  essentially  from  the  for- 
mer. 

Regarding  the  Amceba  from  a  physiological  point  of  view, 
we  see  that,  though  the  animal  nourishes  itself  and  maintains 
its  existence  perfectly,  the  process  of  nutrition  is  carried  on  in 
the  simplest  possible  manner  and  with  the  simplest  possible 
apparatus.  There  is  no  permanent  mouth,  no  stomach  or  ali- 
mentary canal  of  any  kind,  no  respiratory  or  excretory  organs, 
and  even  no  distinct  aperture  for  the  extrusion  of  indigestible 
food.  The  only  distinct  structure  which  is  at  all  concerned  in 
nutrition  is  a  rudimentary  contractile  cavity,  the  first  foreshad- 
owing of  the  heart  in  the  higher  animals.  As  regards  the 
functions  of  relation,  it  is  questionable  how  far  the  Amoeba 
can  be  said  to  have  distinct  perceptions  or  sensations  of  any 
kind.  It  has  no  nervous  system  or  organs  of  sight  or  hearing, 
and  in  all  probability  it  has  nothing  more  than  a  general  sen- 
sibility to  light.  It  appears,  however,  to  be  fully  aware  when 
any  object  comes  in  contact  with  a  pseudopodium,  and  even 
to  have  some  idea  whether  this  is  fit  for  food.  Locomotion, 
as  we  have  seen,  is  entirely  effected  by  the  temporary  pro- 
cesses of  sarcode  or  pseudopodia,  and  there  are  no  permanent 
organs  set  aside  either  for  locomotion  or  for  prehension — that 
is,  for  seizing  external  objects. 

The  only  other  member  of  the  Amoebea  which  deserves 
notice  is  the  Difflugia  (Fig.  3,  5),  which  is  not  uncommonly 
found  in  fresh  water.  Difflugia  in  its  essential  structure 


RHIZOPODA.  33 

does  not  differ  from  the  Amoeba,  but  the  greater  part  of  the 
body  is  enclosed  in  a  sort  of  case  or  carapace,  mostly  com- 
posed of  grains  of  sand,  within  which  the  animal  can  retire 
completely.  The  carapace  is  open  at  one  end,  and  the  pseu- 
dopodia  are  protruded  from  this  aperture.  The  animal  gene- 
rally creeps  about  head-downward,  so  to  speak ;  that  is  to  say, 
with  the  closed  end  of  the  carapace  elevated  above  the  surface 
on  which  it  is  moving. 

ORDER  III.  FORAMINIFERA  (Lat.  foramen,  an  aperture; 
fero,  I  carry).  — The  next  order  of  the  Rhizopoda  is  that  of  the 
Foraminifera,  comprising  animals  which  at  first  sight  appear 
to  be  highly  complex,  but  which  are  really  much  less  highly 
organized  than  the  Amoeba.  The  Foraminifera  may  be  de- 
fined as  Rhizopoda  in  which  the  body  is  protected  by  a  shell 
or  "  test /  "  there  is  no  nucleus  or  contractile  vesicle  /  and  the 
pseudopodia  are  extremely  long  and  threadlike,  and  interlace 
with  one  another  so  as  to  form  a  net-work. 

The  most  obvious  and  striking  character  of  the  Forami- 
nifera is  the  possession  of  an  outer  case  or  shell,  and  for  a  long 
time  they  were  known  to  naturalists  by  then*  shells  alone.  As 
the  shell  or  test  is  usually  very  beautiful  and  often  very  com- 
plex, the  Foraminifera  were  consequently  placed  at  first 
among  the  true  shell-fish  (Mollusca),  very  much  in  advance  of 
their  true  position.  When,  however,  the  anatomical  structure 
of  the  group  came  to  be  investigated,  it  was  soon  found  that 
they  were  really  referable  to  the  Protozoa,  and  that  in  point 
of  fact  they  even  occupy  a  low  position  in  this  sub-kingdom. 
However  elaborate  and  complicated  the  shell  may  be,  the  body 
of  the  contained  animal  is  composed  simply  of  granular  gelati- 
nous sarcode,  highly  elastic  and  contractile,  and  usually  red- 
dish or  yellowish  in  color.  This  sarcode*  not  only  fills  the 
shell,  but  also  in  many  cases  gains  the  exterior  by  means  of 
little  perforations  in  its  walls,  and  forms  a  thin  film  over  its 
outer  surface.  Wherever  the  sarcode  is  exposed,  whether  this 
be  only  at  the  mouth  of  the  shell,  as  in  Miliola  (Fig.  4,  b),  or 
whether  it  be  over  the  whole  surface,  as  in  Discorbina  (Fig.  4, 
c),  it  has  the  power  of  giving  off  pseudopodia.  The  pseudo- 
podia,  however,  differ  greatly  from  those  of  the  Amoeba,  and 
they  show  some  remarkable  characters.  They  are  extremely 
long,  threadlike  processes,  instead  of  being  blunt  and  finger- 
shaped,  and  they  have  the  curious  property  that  they  run  into 
one  another  and  interlace  toward  their  extremities,  so  as  to 
form  a  net-work  which  has  been  aptly  compared  to  an  "  ani- 


34  INVERTEBRATE  ANIMALS. 

mated  spider's  web."  Lastly,  the  microscope  reveals  in  the 
pseudopodia  a  very  curious  circulation  of  minute  solid  parti- 
cles or  granules,  which  travel  in  all  directions  through  the 
pseudopodial  net-work.  Internally,  the  sarcode-body  of  the 
Foraminifera  exhibits  absolutely  no  structures  or  definite  or- 
gans of  any  kind.  Even  the  nucleus  and  contractile  vesicle 
which  occur  in  the  Amoeba  are  here  absent,  and  the  only  traces 
of  structure  are  to  be  found  in  the  existence  of  scattered  gran- 
ules. 

Simple  as  is  the  sarcode-body  of  the  Foraminifera,  it  has 
in  all  cases  the  power  of  secreting  a  skeleton  or  shell,  which 
is  technically  called  the  "test"  (Lat.  testa,  a  shell).  The 
shell  is  usually  "  calcareous  " — that  is  to  say,  composed  of  car- 
bonate of  lime ;  but  it  is  sometimes  "  arenaceous,"  or  com- 
posed of  particles  of  sand  united  together  firmly  by  an  un- 
known animal  cement.  In  either  case,  the  shell  may  exhibit 
one  or  other  of  two  very  distinct  types  of  structure.  In  the 
one  type  (as  in  Miliola,  Fig.  4,  b),  the  shell- walls  are  not  per- 


FIG-  4. — Morphology  of  Foraminifera.  a  Lagena  vulgaris,  a  monothalamous  Foraminifcr ; 
b  Miliola  (after  Schultze),  showing  the  pseudopodia  protruded  from  the  oral  aperture  of 
the  shell ;  c  DiscorMna  (after  Schultze),  showing  the  nautiloid  shell  with  foramina  in 
the  shell- walls,  giving  exit  to  pseudopodia ;  d  Section  of  Nodosaria  (after  Carpenter) ; 
e  Nodosaria  hispida  ;  f  Globige/rina  bulloides, 

forated  with  holes,  and   the  pseudopodia  are    therefore  all 
emitted  from  the  mouth  of  the  shell.     In  the  other  type  (as  in 


RHIZOPODA.  35 

Discorbina,  Fig.  4,  c)  the  shell-walls  are  perforated  with  a 
number  of  little  apertures  or  "  foramina,"  from  which  the  or- 
der derives  its  name.  These  foramina  are  the  mouths  of 
tubes  which  pierce  the  walls  of  the  shell,  and  thus  establish 
a  free  communication  between  the  interior  and  exterior.  In 
this  way  the  sarcode  which  fills  the  inside  of  the  shell  is  en- 
abled to  reach  the  outer  surface,  so  as  to  form  a  film,  from 
any  part  of  which  the  pseudopodia  may  be  given  off.  The 
presence  or  absence  of  foramina  is  believed  to  constitute  a 
true  structural  distinction,  and  the  Foraminifera  may  be 
thereby  divided  into  two  great  groups  (Perforata  and  Im- 
perforata). 

According  to  the  form  of  the  shell,  also,  the  Foraminifera 
may  be  conveniently,  though  arbitrarily,  divided  into  two 
great  sections.  The  simplest  form  of  shell  is  seen  in  such  an 
example  as  Lagena  (Fig.  4,  a),  where  the  shell  consists  of  but  a 
single  chamber ;  and  the  animal,  in  fact,  is  nothing  more  than 
a  little  mass  of  sarcode,  surrounded  by  a  calcareous  envelope. 
Lagena,  then,  may  be  taken  as  the  type  of  what  are  called 
the  "  monothalamous "  Foraminifera  (Gr.  monos,  single ; 
thalamos,  a  chamber) — that  is  to  say,  of  those  forms  in  which 
the  animal  consists  of  a  single  segment,  and  the  shell  of  a 
single  chamber.  All  the  Foraminifera  without  exception 
commence  life  as  "  simple  "  or  "  monothalamous  "  forms,  like 
Lagena^  but  it  is  comparatively  seldom  that  they  retain  this 
simplicity  throughout  life.  In  the  great  majority  of  cases  the 
primitive  mass  of  sarcode  commences  a  process  of  budding, 
or  "  gemmation,"  by  which  it  becomes  converted  from  a  "sim- 
ple "  into  a  "  compound  "  form.  The  original  sarcode-mass, 
that  is  to  say,  begins  to  throw  out  buds  in  some  determinate 
direction;  all  the  buds  thus  produced  remaining  connected 
with  one  another,  and  all  surrounding  themselves  with  a  cal- 
careous covering.  In  this  way  we  get  ultimately  a  compound 
organism,  composed  of  a  number  of  little  masses  of  sarcode, 
all  permanently  united  to  one  another,  and  all  enclosed  in  a 
common  shell.  We  get  then,  ultimately,  such  a  form  as  N~o- 
dosaria  (Fig.  4,  d,  e),  which  may  be  regarded  as  a  good  example 
of  these  so-called  "  compound  "  or  "  polythalamous  "  Fora- 
minifera  (Gr.  polm,  many ;  thalamos,  a  chamber).  The  exact 
form  of  shell  which  is  produced  by  this  process  of  budding 
will  depend  upon  the  direction  in  which  the  buds  are  given 
off  by  the  primordial  segment.  If  the  buds  are  given  off  in  a 
line,  we  get  such  a  form  as  Nodosaria.  If  they  are  given  off 
in  a  spiral  direction,  each  succeeding  segment  being  a  little 


36  INVERTEBRATE  ANIMALS. 

larger  than  the  one  before  it,  and  the  coils  of  the  spiral  all 
lying  in  one  plane,  then  we  get  such  a  shell  as  DiscorMna 
(Fig.  4,  c).  This  is  one  of  the  commonest  forms  of  shell  among 
the  Foraminifera,  and  it  is  often  called  the  "  nautiloid  "  shell, 
from  the  close  resemblance  which  it  bears  in  shape  to  the 
well-known  shell  of  the  pearly  Nautilus.  It  was,  in  fact,  this 
external  similarity  which  induced  the  older  naturalists  to 
place  the  Foraminifera  among  the  Mollusca  in  the  neighbor- 
hood of  the  cuttle-fishes.  There  are  numerous  other  types  of 
shell,  all  of  which  can  be  referred  to  the  manner  in  which 
gemmation  is  carried  on  by  the  primordial  segment ;  but  the 
two  forms  above  mentioned  may  be  taken  as  sufficient  ex- 
amples. It  may  be  mentioned,  however,  that  there  are  forms 
in  which  the  new  segments  are  added  in  a  very  irregular  man- 
ner, and  the  resulting  colony  has  no  very  definite  shape,  as  in 
Globigerina  (Fig.  4,/). 

AFFINITIES  OF  THE  FORAMINIFERA. — In  spite  of  their  beautiful,  and  in 
many  cases  complex,  shells,  the  anatomical  structure  of  the  Foraminifera  is  so 
simple  that  it  may  fairly  be  questioned  whether  in  a  systematic  arrangement 
they  should  not  be  placed  at  the  bottom  of  the  whole  sub-kingdom  Protozoa. 
Perhaps  the  nearest  relatives  of  the  Foraminifera  are  the  Polycystina,  a 
group  of  organisms  which  we  have  yet  to  consider.  These  differ  from  the 
Foraminifera  in  little  or  nothing,  except  that  the  shell  is  composed  of  flint. 
The  Foraminifera  are  also  clearly  related  to  those  forms  of  the  Amcebea 
which  possess  shells,  such  as  Diffluffia.  The  sarcode-body  of  Difflugia, 
however,  contains  a  nucleus  and  a  contractile  vesicle,  and  the  pseudopodia 
are  thick  and  blunt,  so  that  the  differences  are  sufficiently  weighty.  There 
are  also  very  interesting  points  of  relationship  between  the  Foraminifera 
and  the  sponges,  which  cannot  be  touched  upon  here.  A  few  words,  how- 
ever, may  be  said  on  the  physiological  deductions  which  may  be  drawn  from 
the  study  of  the  Foraminifera.  Regarded  from  a  physiological  point  of 
view,  the  structural  simplicity  of  the  Foraminifera  renders  them  all  the 
more  wonderful.  We  have  in  them  the  great  equation  of  life  presented  to 
us  in  perhaps  its  simplest  form.  They  are  composed  of  an  organic  substance, 
but  cannot  be  said  to  possess  "  organization,"  being  "  structureless,  and 
without  permanent  distinction  or  separation  of  parts."  *  Nevertheless  they 
perform  all  the  physiological  functions ;  they  assimilate  food — they  live, 
grow,  and  maintain  their  integrity  in  the  face  of  the  destructive  forces  con- 
stantly at  work  upon  them — they  reproduce  their  like — and  they  have  cer- 
tain relations  with  the  external  world,  being  at  any  rate  capable  of  indepen- 
dent locomotion.  All  these  vital  actions  they  effect  without  possessing  a 
single  organ  permanently  set  apart  for  the  performance  of  any  one  of  them. 
Lastly,  they  have  the  power  of  building  up  an  outer  envelope  or  shell,  which 
is  always  beautiful,  and  is  often  of  the  most  complex  character,  and  con- 
structed upon  a  regular  mathematical  plan.  The  Foraminifera,  then,  of  all 
known  animals,  offer  the  most  convincing  illustration  of  two  laws  :  firstly, 
that  there  is  something  in  the  action  and  nature  of  vital  forces  altogether 
distinct  from  any  thing  hitherto  observed  in  the  physical  forces  ;  and  sec- 

*  Huxley. 


RHIZOPODA.  37 

ondly,  that  life  is  the  cause  of  organization,  and  not  the  result  of  it :  in  other 
words,  an  animal  is  organized,  or  possesses  structure,  because  it  is  alive ;  it 
does  not  live  because  it  is  organized. 

DISTRIBUTION  OF  FORAMINIFERA  m  SPACE.* — The  Foraminifera  are  ex- 
clusively marine  or  inhabitants  of  the  ocean,  and  have  a  world-wide  distribu- 
tion. They  are  mostly  very  minute,  but  some  of  vhe  extinct  forms  attained 
a  size  of  as  much  as  three  inches  in  circumference  (e.  g.,  the  Nummulite, 
Fig.  5).  Some  forms  may  be  obtained  adhering  to  the  roots  of  tangle  (Lami- 
niria)  at  or  near  low-water  mark,  but  they  are  mostly  to  be  dredged  from  tol- 
erably deep  water.  In  the  deepest  parts  of  the  ocean  which  have  yet  been 
examined  by  the  dredge — at  a  depth,  namely,  of  nearly  three  miles — Forami- 
nifera have  been  obtained  in  abundance.  There  is  also  no  doubt  that  in 
many  parts  of  the  deep  ocean,  especially  where  warm  currents  exist,  there 
are  now  forming  deposits  of  the  shells  of  Foraminifera,  which  may  well  be 
compared  to  the  great  masses  of  white  chalk  with  which  the  geologist  is 
familiar.  Foraminifera  may  generally  be  obtained  for  examination  from  the 
shakings  of  sponges  or  from  the  sand  of  the  sea-shore,  especially  in  warm 
climates.  To  give  some  idea  of  their  abundance,  it  may  be  stated  that  Plan- 
cus  found  about  6,000  specimens  in  an  ounce  of  sand  from  the  Adriatic  ;  but 
D'Orbigny  calculated  that  no  fewer  than  between  three  and  four  millions 
were  present  in  an  ounce  of  sand  from  the  Caribbean  Sea. 

DISTRIBUTION  OF  FORAMINIFERA  IN  TIME. — It  is  not  the  object  of  the 
present  work  to  enter  into  the  consideration  of  the  past  existence  of  differ- 
ent groups  of  animals,  since  this  presupposes  some  knowledge  of  geology, 
but  the  Foraminifera  present  some  points  of  special  interest  which  may  be 
very  shortly  noticed.  In  the  first  place,  as  far  as  is  yet  known,  the  Forami- 
nifera were  the  earliest  and  oldest  of  created  beings.  The  oldest  fossil 
which  has  hitherto  been  exhumed  by  the  labors  of  geologists  is  believed  to 
have  been  a  Foraminifer,  \  of  large  size,  and  with  some  decided  affinities  to 
existing  forms.  In  the  second  place,  it  is  only  by  an  examination  of  the  dis- 
tribution of  the  Foraminifera  in  past  time  that  we  can  arrive  at  any  ade- 
quate notion  of  the  importance  of  these  microscopic  creatures  when  looked 
at  in  the  aggregate.  The  great  geological  formation  known  as  the  white 
chalk — a  formation  which  forms  the  well-known  chalk-cliffs  of  the  south  of 
England,  and  which  stretches  over  a  great  part  of  the  continent  of  Europe, 
attaining  sometimes  a  thickness  of  not  less  than  600  feet — is  almost  wholly 
composed  of  the  shells  of  Foraminifera,  visible  only  to  the  microscope.  The 
smallest  fragment  of  the  common  chalk,  with  which  every  one  is  familiar, 
contains  numbers  of  these  minuta  shells ;  and  it  is  a  singular  fact  that  some 
of  the  species  in  the  chalk  are  indistinguishable  from  forms  which  now  oc- 
cur in  the  ooze  which  forms  the  bed  of  the  Atlantic  at  great  depths.  The 
stone  of  which  Paris  is  built  is  to  a  very  great  extent  composed  of  the  shells 
of  Foraminifera,  especially  of  the  Miliola  ;  and  it  is  hardly  an  exaggeration 
to  say  that  Paris  is  mainly  built  up  out  of  these  minute  organisms.  Another 
remarkable  formation  is  that  known  as  the  "  Nummulitic  limestone,"  from 
the  presence  in  it  of  a  large  coin-shaped  Foraminifer,  the  Nummulite  (Fig. 
5),  generally  about  as  large  as  a  shilling. 

The  Nummulitic  limestone  stretches  from  France  on  the  west  to  the  fron- 
tiers of  China  on  the  east,  and  is  almost  everywhere  readily  recognizable  as 

*  Under  the  term  " Distribution  in  Space"  come  all  the  facts  relating  to  the  present 
occurrence  of  any  animal  or  group  of  animals  upon  the  globe.  Under  the  term  "  Distribu- 
tion in  Time  "  come  all  the  facts  relating  to  the  past  occurrence  of  any  animal  or  group  of 
animals  upon  the  globe. 

t  The  Eozoon  Canadense  of  the  Laurentian  Eocks  of  Canada. 
3 


38  INVERTEBRATE  ANIMALS. 

a  distinct  formation.  It  attains  in  places  a  thickness  of  several  thousand 
feet,  and  is  especially  largely  developed  in  the  Alps.  It  has  an  historic  in- 
terest from  the  fact  that  the  Pyramids  are  built  of  it,  and  that  the  Nummu- 
u'tes  in  it  were  noticed  by  Herodotus,  the  "  father  of  history." 


FIG.  5. — Nummulites  Ic&vigatug. 

ORDER  IV.  RADIOLARIA  (Lat.  radius,  a  ray). — The  third 
order  of  the  Ehizopoda  is  that  of  the  Radiolaria,  essentially 
distinguished  by  the  fact  that  the  sarcode-body  has  the  power 
of  secreting  a  "  siliceous  "  or  flinty  skeleton,  either  in  the  form 
of  a  shell,  or  of  detached  spicules  or  needles ;  while  the  pseu- 
dopodia  are  long  and  thread-like,  and  stand  out  from  the  body 
like  rays.  In  this  last  character  the  Radiolaria  approach 
very  closely  to  the  Foraminifera ;  and  the  resemblance  be- 
tween the  two  groups  is  still  further  increased  by  the  fact 
that  the  pseudopodia  often  run  into  one  another  so  as  to  form 
a  net-work,  and  sometimes  show  a  circulation  of  granules 
along  their  edges.  Three  groups  of  organisms  have  been 
described  as  belonging  to  the  Radiolaria,  and  we  may  briefly 
notice  an  example  of  each  of  these. 

In  the  first  family  we  have  organisms  like  Acanthometra 
(Fig.  6,  «),  in  which  the  body  is  composed  of  sarcode,  sup- 
ported by  a  framework  of  siliceous  or  flinty  rods,  which  all 
meet  in  a  common  centre.  The  spines  or  rods  are  all  perfo- 
rated by  canals,  and  each  conveys  a  pseudopodium,  which  is 
protruded  from  an  aperture  at  its  apex.  Many  pseudopodia, 
however,  are  given  off  from  the  surface  of  the  body  directly, 
and  are  not  enclosed  in  the  spines.  The  Acanthometrce  are 
all  minute,  and  are  found  floating  near  the  surface  in  the  open 
ocean,  sometimes  in  great  numbers. 

In  the  second  family  (Polycystina,  Fig.  6,  b)  we  have  a 
number  of  beautiful  little  organisms  closely  allied  to  the  Fo- 
raminifera, but  differing  in  the  fact  that  the  body  is  enclosed 
in  a  glassy  shell  composed  of  flint.  The  shell  is  perforated 
by  numerous  holes  through  which  the  pseudopodia  are 
emitted,  and  it  is  usually  of  extreme  beauty,  being  sculptured 


RHIZOPODA. 


39 


in  various  ways,  and  often  adorned  with  spines.  The  sarcode 
of  the  body  is  usually  olive  brown  in  color,  and  often  does 
not  quite  fill  the  shell. 


FIG.  6.—  a  AeantJiometra  lanceolata  ;  ~b  Ilaliomma  Jiexacanthum,  one  of  the  Polycys- 
tina  (after  Miiller). 

The  pseudopodia  are  filamentous,  and  exhibit  a  slow  cir- 
culation of  granules  along  their  borders,  but  they  do  not  run 
into  one  another.  All  the  Potycystina  are  microscopic,  and 
they  are  all  inhabitants  of  the  sea.  They  are  best  known  to 
students  of  the  microscope  as  the  "  Fossil  Infusoria  of  Barba- 
does,"  as  they  occur  in  incalculable  numbers  in  a  sandstone  in 
that  island. 

In  the  third  family  (Thalassicottida,  Fig.  7)  are  included 
a  number  of  singular  gelatinous'  organisms  which  may  be  as 
large  as  an  ordinary  marble,  but  are  often  hardly  visible  to 
the  unassisted  eye.  They  are  found  floating  passively  at  the 
surface  of  most  seas. 

The  body  in  all  the  Thalassicollida  is  composed  of  sarcode, 
and  has  the  power  of  giving  off  thread-like  radiating  pseudo- 
podia,  which  sometimes  run  into  one  another  and  form  net- 
works. In  all  cases  the  sarcode-body  appears  to  have  the 
power  of  secreting  flint  in  some  form  or  other.  In  Cotto- 
sphcera  (Fig.  7,  «),  the  flint  is  secreted  in  the  form  of  a  shell 
or  test,  perforated  by  large  apertures.  In  Thalassicolla  (Fig. 
7,  #),  the  silica  forms  groups  of  needles  or  "  spicula,"  scattered 
here  and  there  in  the  ell-like  sarcode. 


OKDER  IV.  SPOXGIDA.  —  The  last  order  of  the  Rhizopoda 
is  that  of  the  Spongida,  the  exact  nature  and  position  of 
which  have  only  recently  been  determined.  For  a  long  time 
sponges  were  pretty  generally  regarded  as  being  vegetables, 
and  it  is  only  since  the  microscope  has  been  employed  in  their 


40 


INVERTEBRATE   ANIMALS. 


elucidation  that  their  true  nature  has  been  made  out.  Most 
naturalists  are  now  agreed  as  to  the  propriety  of  placing  the 
sponges  in  the  animal  kingdom,  and  they  are  generally  re- 
ferred to  the  Rhizopoda,  though  they  are  sometimes  looked 
upon  as  constituting  a  distinct  and  separate  class  of  the  Pro- 
tozoa. The  apparent  complexity  of  structure  which  the 
sponges  exhibit  is  due  to  the  fact  that  what  we  ordinarily 


FIG.  7. — a  Siliceous  shell  of  Collofphcera ;  b  Thalassicolla,  showing  the  radiating  pseudo- 
podia  and  groups  of  siliceous  spicula  (after  Miiller). 

term  a  sponge  is  really  a  colony  or  aggregation  of  separate 
masses  of  sarcode,  greatly  resembling  Amoebae  in  structure, 
and  having  the  power  of  secreting  a  skeleton  or  supporting 
framework  common  to  the  whole  assemblage.  Sponges,  in 
fact,  may  be  denned  as  compound  Rhizopoda,  forming 
masses  which  are  traversed  by  canals  opening  on  the  surface, 
and  supported  by  aframeicork  of  horny  fibres  or  of  calcare- 
ous or  flinty  needles. 

There  are,  then,  two  essential  elements  in  the  structure  of 
a  sponge — namely,  the  sarcode-bodies  which  constitute  the 
animal  itself,  and  which  are  collectively  termed  the  "  sponge- 
flesh,"  and  the  hard  framework  or  "  skeleton  "  upon  which  the 
flesh  is  supported.  To  understand  the  nature  of  these  fully, 
we  may  take  an  ordinary  horny  sponge,  such  as  we  are  con- 
stantly in  the  habit  of  using.  As  we  see  the  sponge  in  this 
country,  we  are  only  acquainted  with  the  skeleton,  which  is 
composed  of  an  enormous  number  of  horny  fibres,  all  interlaced 
and  interwoven  with  one  another,  but  leaving  numerous  holes 
and  canals  between  their  bundles  (Fig.  9,  d).  In  its  living 
condition,  however,  the  whole  of  this  skeleton  is  covered  in- 
side and  outside — saturated,  in  fact — with  a  kind  of  slimy  ma- 
terial very  like  white-of-egg  to  look  at.  This  is  the  so-called 
sponge-flesh,  and,  upon  examining  this  with  a  microscope,  it 
is  found  to  be  composed  of  an  enormous  number  of  minute 


RHIZOPODA. 


41 


masses  of  sarcode,  all  more  or  less  completely  independent 
of  each  other,  and  each  very  closely  resembling  an  Amoeba. 
These  separate  "  sponge-particles,"  or  "  sarcoids,"  as  they  are 
called,  consist,  in  fact,  of  granular  sarcode,  capable  of  pushing 
out  little  processes  or  threads  of  sarcode  in  the  form  of  pseudo- 
podia,  and  sometimes  furnished  with  an  internal  solid  mass  or 
nucleus  (Fig.  3,  c).  In  some  cases  each  sarcoid  carries  a 
single  lash-like  vibrating  filament  or  cilium  (Fig.  3,  <#,  e). 
Each  sarcoid  has  the  power,  if  detached,  of  independent  move- 
ment, and  each  can  obtain  food  for  itself.  As  the  sponge, 
however,  is  a  fixed  animal,  some  provision  is  necessary  by 
which  food  shall  be  conveyed  to  the  sarcoids  in  the  interior  of 
the  mass.  This  is  effected  by  a  remarkable  water-carrying  or 
"aquiferous"  system  in  the  following  manner:  The  entire 
sponge  is  riddled  in  every  direction  by  an  immense  number 
of  canals,  all  opening  on  the  surface,  and  communicating  freely 


FIG.  8. — Diagrammatic  section  of  Spongilla  (after  Huxley),  a  a  Outer  or  superficial  layer 
of  the  sponge ;  b  b  Inhalant  apertures,  or  "  pores ; "  c  c  Ciliated  chambers ;  d  An  exha- 
lant  aperture,  or  "  osculurn."  The  arrows  indicate  the  direction  of  the  currents. 

with  one  another  in  the  interior  of  the  mass.  The  canals  are 
of  different  sizes,  and,  as  can  readily  be  observed  in  an  ordinary 
sponge,  their  external  openings  are  also  of  different  sizes.  A 
few  of  the  holes  are  of  much  larger  size  than  the  others,  and 
these,  for  reasons  which  will  be  seen  directly,  are  called  the 
"  exhalant  apertures,"  or  "  oscula."  The  great  majority  of  the 
holes  are  very  minute,  and  these  are  known  as  the  "  inhalant 
apertures,"  or  "  pores."  In  a  living  sponge  a  more  or  less 
constant  circulation  of  water  is  carried  on  by  means  of  this 
canal  system.  The  water  is  admitted  by  means  of  the  pores 
(Fig.  8,  b  #),  is  driven  into  the  interior  of  the  sponge,  and  is 
finally  expelled  in  steady  streams  from  the  oscula  (Fig.  8,  d). 
The  mechanism  by  which  this  circulation  of  water  is  effected, 


42 


INVERTEBRATE  ANIMALS. 


was  long  unknown,  but  it  is  now  known  to  consist  in  aggrega- 
tions of  sponge-particles  provided  with  cilia  which  all  work 
toward  the  interior  of  the  sponge  (Fig.  8,  c  c).  The  circula- 
tion of  water  in  this  manner  can  be  readily  observed  in  many 
of  our  common  marine  sponges,  and  it  is  under  the  control  of 
the  animal  to  a  great  extent.  The  large  apertures  or  oscula 
are  permanent,  but  they  can  be  closed  and  opened  at  will ; 
while  the  smaller  apertures  or  pores  appear  to  be  formed 
afresh,  wherever  they  are  wanted,  at  any  point  of  the  surface. 
By  means  of  the  currents  of  water  each  individual  sarcoid  or 
sponge-particle  is  enabled  to  obtain  food,  so  that  the  whole 
sponge,  as  remarked  by  Huxley,  "  represents  a  kind  of  sub- 
aqueous city,  where  the  people  are  arranged  about  the  streets 
and  roads  in  such  a  manner  that  each  can  easily  appropriate 
his  food  from  the  water  as  it  passes  along."  It  is  also  not 
improbable  that  the  process  is  at  the  same  time  a  rudimentary 
form  of  respiration. 


4*10.  9.— ft  Gemmule  of  Spongilla\  7t  Hilum;  &  Diagrammatic  section  of  the  gemmule* 
showing  the  outer  layer  of  spicules  or  amphidiscs,  and  the  inner  mass  of  cells ;  h  Hilum ; 
c  One  of  the  amphidiscs  seen  in  profile ;  d  Fragment  of  the  skeleton  of  a  horny  sponge 
(after  Bowerbank),  showing  the  interlacing  horny  fibres  with  spicula.  All  much  magni- 
fied. 

Such,  then,  are  the  general  phenomena  exhibited  by  any 
sponge,  and  the  chief  variations  which  occur  among  the 
sponges  are  to  be  found  in  the  nature  of  the  skeleton.  In  the 
sponges  of  commerce  the  skeleton  consists  of  matted  fibres 
composed  of  a  substance  nearly  allied  to  horn.  In  other  forms 
the  skeleton  is  calcareous,  or  composed  of  lime;  and  in  other 
cases,  again,  it  is  siliceous,  or  composed  of  flint.  The  Venus's 
flower-basket  (Euplectella),  which  looks  like  a  goblet  woven 


RHIZOPODA.  43 

of  spun  glass,  is  a  familiar  example  of  the  flinty  sponges.  In 
most  cases,  the  skeleton,  and  often  the  flesh  as  well,  is  fur- 
nished with  more  or  less  numerous  needles  or  spicula,  gener- 
ally of  flint,  but  sometimes  of  lime,  which  assume  a  great  vari- 
ety of  shapes,  and  appear  to  exercise  different  functions  (Fig. 
9,  c,  d). 

As  regards  the  reproductive  process  in  the  sponges,  it  will 
be  sufficient  to  state  very  briefly  the  leading  phenomena  which 
have  been  observed  in  the  fresh-water  sponge  (Spongilla 
flumatilis).  If  a  specimen  of  Spongilla  be  observed  toward 
the  approach  of  winter,  its  deeper  portions  will  be  found  to  be 
filled  with  numerous  small,  rounded  bodies,  like  seeds,  which 
have  been  called  "  gemmules."  Each  gemmule  (Fig.  9,  a,  b) 
exhibits  at  one  point  a  small  aperture,  and  is  found  to  be  com- 
posed of  a  leathery  membrane,  surrounded  by  a  layer  of  sar- 
code,  in  which  are  imbedded  a  number  of  spicula.  These 
spicula  consist  each  of  a  central  rod  or  axle  carrying  a  toothed 
wheel  or  disk  at  each  end  (Fig.  9,  c).  In  the  interior  of  the 
capsule  thus  formed  is  a  mass  of  cells,  of  which  the  central 
ones  contain  numerous  reproductive  germs.  When  the  spring 
comes,  these  masses  are  discharged  into  the  water  through  the 
aperture  of  the  gemmule,  and  become  developed  into  fresh 
Spongillce.  In  addition  to  this  method  of  reproduction,  the 
fresh-water  sponge  during  the  summer  months  has  the  power 
of  producing  true  eggs  or  ova,  and  sperm-cells.  The  impreg- 
nated ova  develop  themselves  into  embryos,  which  are  pro- 
vided with  numerous  cilia  or  vibrating  hairs,  by  means  of 
which  they  swim  about  freely.  Finally,  upon  finding  a  suit- 
able locality,  they  fix  themselves  to  some  solid  object,  lose 
their  cilia,  and  grow  up  into  Spongillce.  Indeed,  as  a  general 
if  not  universal  rule,  the  embryos  of  the  sponges  are  provided 
with  cilia,  and  are  thus  capable  of  active  locomotion.  In  this 
way  is  secured  the  extension  over  a  wide  area  of  these  other- 
wise fixed  and  plant-like  organisms. 

Distribution  of  Sponges  in  Space. — It  remains  only  to  add 
a  few  words  on  the  distribution  of  sponges  in  space.  With 
the  single  exception  of  Spongilla,  all  known  sponges  are  in- 
habitants of  the  sea ;  but  the  former  is  to  be  found  in  lakes 
and  rivers  in  most  parts  of  the  world.  The  marine  sponges 
are  found  mostly  attached  to  stones  and  other  foreign  objects 
between  tide-marks  and  in  deep  water.  The  sponges  of  com- 
merce are  mostly  obtained  from  the  Grecian  Archipelago,  but 
inferior  kinds  are  imported  from  the  Bahama  Islands.  One 
common  sponge  ((7/wwa),  instead  of  incrusthig  other  objects, 


44  INVERTEBRATE  ANIMALS. 

inhabits  branching  cavities  in  shells,  which  it  excavates  for 
itself.  It  apparently  lives  upon  the  animal  matter  contained 
in  the  shell,  and  few  oyster-shells  can  be  picked  up  upon  our 
shores  which  do  not  exhibit  the  perforations  and  mines  of 
some  species  or  other  of  this  genus.  Fossil  shells,  also,  often 
occur,  which  show  that  these  mining  sponges  have  enjoyed  a 
vast  antiquity. 


CHAPTER  III. 
INFUSORIA. 

THE  last  class  of  the  Protozoa  is  that  of  the  Infusoria,  so 
called  because  of  their  being  frequently  developed  in  organic 
infusions  under  the  following  singular  circumstances :  If  some 
water  be  taken,  and  any  animal  or  vegetable  substance  be 
soaked  or  boiled  in  it,  a  solution  is  formed  containing  organic 
matter,  or,  in  other  words,  an  "  organic  infusion."  It  is  un- 
necessary to  say  that  if  this  infusion  be  examined  under  the 
microscope,  after  boiling,  nothing  will  be  detected  in  it — 
nothing  living,  at  any  rate.  If  examined,  however,  at  the  end 
of  a  few  days'  time — if  the  circumstances  have  been  favor- 
able— a  vast  number  of  living  forms  will  now  be  found  in  it. 
Among  these  will  be  found  several  of  the  members  of  the 
present  class,  and  hence  the  name  applied  to  them  of  Infusorian 
animalcules,  or  Infusoria.  It  is  unnecessary  to  enter  here 
into  the  question  how  these  living  beings  are  produced,  since 
the  subject  is  one  of  great  obscurity,  and  opinions  are  still 
divided  upon  it.  It  is  sufficient  to  remark  that  there  are  emi- 
nent observers  who  hold  that  the  appearance  of  the  Infusoria 
in  this  fashion  is  to  be  explained  upon  the  theory  that  they 
have  been  spontaneously  produced  out  of  the  inorganic  ma- 
terials of  the  infusion,  in  opposition  to  the  general  view  that 
they  are  derived  from  preexistent  germs. 

The  position  of  the  Infusoria  is  somewhat  doubtful,  and 
it  appears  probable  that  they  will  ultimately  have  to  be  re- 
garded as  a  separate  sub-kingdom,  or  as  a  branch  of  a  higher 
sub-kingdom  (Annuloida).  In  the  mean  while  it  is  most  con- 
venient to  retain  them  in  their  present  place,  at  the  head  of 
the  sub-kingdom  Protozoa.  Regarded  in  this  light,  the  In- 
fusoria present  a  great  advance  in  structure  over  all  the 
forms  which  wre  have  hitherto  studied — an  advance  which  is 
especially  seen  in  the  constant  presence  of  a  permanent 


46 


INVERTEBRATE  ANIMALS. 


mouth.  The  Infusoria  may  be  defined  as  Protozoa,  which 
are  provided  with  a  mouth,  and  generally  .a  rudimentary 
digestive  canal.  They  do  not  possess  the  power  of  emitting 
pseudopodia,  but  are  furnished  with  vibratile  cilia  or  con- 
tractile filaments.  They  are  mostly  microscopic  in  size,  and 
their  bodies  usually  consist  of  three  distinct  layers.  They 
are  mostly  simple  free-swimming  organisms,  but  they  some- 
times form  colonies  by  budding,  and  are  fixed  to  some  solid 
object  in  their  adult  condition.  As  types  of  these  two  sec- 
tions of  the  Infusoria,  we  may  take  respectively  Paramcecium 
and  Epistylis. 

Paramoecium  (Fig.  10)  is  a  beautiful  slipper-shaped  little 


FIG.  10. — Ciliated  Infusoria.  A.  Paramo&cium,  showing1  the  nucleus  (n)  and  two  con- 
tractile vesicles  (»);  B.  Paramo&cium  bursaria  (after  Stein),  dividing1  transversely, 
n  Nucleus ;  n'  nucleolus ;  v  Contractile  vesicle ;  C.  Paramoecium  aurelia  (after  Ehren- 
berg),  dividing  longitudinally. 

creature,  which  may  be  found  commonly  in  stagnant  waters 
or  in  artificially-prepared  infusions.  The  body  is  nearly  quite 
transparent,  and  consists  of  three  layers — 1.  A  structureless, 
transparent,  external  film  or  pellicle ;  2.  A  central  mass  of  soft 
semi-fluid  sarcode ;  and  3.  An  intermediate  layer  of  firm  and 
consistent  sarcode.  The  external  membrane  or  cuticle  is 
richly  covered  with  minute  vibrating  hairs  or  cilia,  which  ap- 
pear, however,  to  be  really  derived  from  the  middle  layer. 
The  cuticle  is  also  perforated  by  the  aperture  of  the  mouth, 
which  is  continued  into  a  short,  funnel-shaped  gullet.  The 
gullet,  however,  is  not  continued  into  any  distinct  stomach, 
but  opens  directly  into  the  soft,  semi-fluid  sarcode  which  con- 
stitutes the  central  abdominal  cavity.  The  particles  of  food 


INFUSORIA.  47 

on  passing  through  the  gullet  are  directly  received  into  the 
central  mass  of  diffluent  sarcode,  where  they  undergo  a  kind  of 
slow  circulation  or  rotation.  As  in  the  case  of  the  Amoeba, 
each  particle  of  food  generally  carries  with  it  a  little  water,  so 
that  the  appearance  is  produced  of  a  number  of  little  clear 
spaces  in  the  central  sarcode.  These  are  now  called  vacuoles, 
or  food-vacuoles ;  but  they  were  originally  described  by  Ehren- 
berg,  the  famous  Prussian  microscopist,  as  so  many  distinct 
stomachs,  in  consequence  of  which  he  named  the  Infusoria  the 
Polygastrica  (Gr.  polus,  many;  and  g aster,  stomach).  The 
vibrating  cilia  which  clothe  the  surface  of  Paramcecium  serve 
partly  to  drive  the  animal  rapidly  through  the  water,  and  partly 
to  set  up  currents  by  means  of  which  food  is  conveyed  to  the 
mouth.  All  the  nutrient  particles  obtained  in  this  way  undergo 
the  circulation  in  the  central  sarcode  above  spoken  of,  where 
they  are  partially  or  completely  digested.  The  indigestible 
portions  of  the  food  appear  to  be  got  rid  of  by  a  second  aper- 
ture (anus)  placed  near  the  mouth.  The  only  other  organs 
possessed  by  Paramcecium  are  the  so-called  nucleus  and 
nucleolus,  and  the  contractile  vesicle  (or  vesicles),  all  of  which 
appear  to  be  situated  in  the  cortical  layer  of  the  body.  The 
nucleus  (Fig.  10,  n)  is  a  little  solid  body,  composed  of  an  ex- 
ternal membrane,  with  granular  contents,  and  having  the 
nucleolus  (n')  firmly  attached  to  its  exterior  in  the  form  of  a 
little  spherical  particle.  Both  appear  to  be  organs  of  repro- 
duction, the  nucleus  being  an  ovary,  and  the  nucleolus  a 
spermarium.  The  names,  therefore,  of  nucleus  and  nucleolus 
are  extremely  inappropriate,  as  they  lead  to  confusion  with  the 
wholly  distinct  structures  which  receive  these  names  in  an 
ordinary  animal  or  vegetable  cell.  The  contractile  vesicle  (v)  has 
exactly  the  same  structure  as  in  the  Amoeba.  It  is  simply  a 
little  contractile  cavity  filled  with  a  fluid  apparently  derived 
from  the  digestion,  and  contracting  and  dilating  at  regular 
intervals.  There  is  usually  only  a  single  vesicle  present,  but 
there  may  be  two  or  more. 

Reproduction  in  Paramoecium  may  be  effected  by  fission — 
that  is  to  say,  by  a  simple  splitting  of  the  body  of  a  single  in- 
dividual into  two  portions,  each  of  which  becomes  a  fresh 
being.  The  process  of  fission  may  commence  at  the  surface, 
or  it  may  begin  at  the  nucleus.  In  other  cases,  two  Para- 
mcecia  come  together  and  adhere  closely  to  one  another.  The 
nucleus  and  nucleolus  enlarge,  and  the  nucleolus  of  each  is 
transferred  to  the  other,  apparently  through  the  mouth.  As 
the  result  of  this,  numerous  germs  are  produced,  which,  after 


48 


INVERTEBRATE   ANIMALS. 


their  liberation  from  the  body  of  the  parent,  are  developed 
into  fresh  individuals. 

Epistylis,  which  is  a  good  example  of  the  fixed  Infusoria, 
may  be  regarded  as  essentially  similar  to  JParamoecium  in  its 
anatomical  structure.  In  place,  however,  of  a  single  free- 
swimming  organism,  we  have  now  a  colony  of  more  or  less 
closely  related  beings,  the  whole  assuming  a  plant-like  form, 
and  being  rooted  to  some  solid  object.  The  colonies  of 
Epistylis  may  not  uncommonly  be  found  adhering  to  the 
stems  of  water-plants  or  to  the  backs  of  our  common  water- 
beetles,  and  the  trained  eye  readily  recognizes  them  as  a 
grayish-white  down  or  nap.  On  placing  a  portion  of  this 
under  the  microscope,  we  see  a  number  of  little  oval  cups  or 
"  calyces  "  supported  upon  a  branched  stem.  Each  cup  con- 
tains a  sarcode-body,  essentially  the  same  as  Paramcecium 
in  structure,  consisting  of  granular  sarcode,  with  vacuoles,  a 
nucleus,  and  a  contractile  vesicle.  The  end  of  the  cup  farthest 
from  the  stalk  terminates  in  a  rounded  aperture,  through 
which  there  can  be  protruded  a  ciliated  disk.  On  one  side 
of  this  disk  is  the  aperture  of  the  mouth,  leading  into  a  kind 
of  gullet,  which  is  also  furnished  with  large  vibrating  cilia. 
This,  in  turn,  opens  directly  into  the  soft,  granular  sarcode 
of  the  abdominal  cavity,  which  exhibits  a  constant  though 
slow  rotation. 


FIG  11  —Ciliated  Infusoria,     a  Vagimcola ;  ft  Stcmtor  Jfulltri,  the  Trumpet  Animalcule; 
c  Group  of  Vorticellue ;  d  Detached  bud  of  Vorticella. 

A  still  commoner  and  equally  beautiful  example  of  the 
Stalked  Infusoria  is  the  so-called  Bell-animalcule  (  Vorticella. 
Fig.  11,  c),  which  may  be  found  hi  any  stagnant  pool  attached 


INFUSORIA.  49 

to  the  stems  of  aquatic  plants.  The  body  in  "Vorticella  forms 
a  kind  of  cup  or  "  calyx  "  supported  upon  a  long  stalk,  which 
is  in  turn  fixed  to  some  solid  object.  The  stem  contains  a 
contractile  fibre  in  its  interior,  and  the  animal  can  by  this 
means  push  itself  out  or  coil  itself  up  with  the  utmost  rapidity. 
The  vibrating  filaments  or  cilia  are  not  scattered  over  the 
whole  surface  of  the  bell-shaped  body,  but  are  collected  to 
form  a  kind  of  fringe  or  circle  round  the  mouth  of  the  calyx. 
Nearly  in  the  centre  of  this  ring,  or  on  one  side,  is  placed  the 
aperture  of  the  mouth,  which  leads  by  a  short  gullet  straight 
into  the  central  soft  sarcode  of  the  interior  of  the  body.  A 
nucleus  and  contractile  vesicle  are  also  present,  so  that  in  the 
essential  points  of  its  anatomy  Vorticella  does  not  differ  from 
a  free-swimming  Infusorian  such  as  Paramcecium.  Indeed,  a 
transition  between  the  two  forms  is  found  in  the  so-called 
Trumpet  animalcule  or  Stentor  (Fig.  11,  #),  which  can  detach 
itself  and  swim  about  at  will,  at  the  same  time  that  it  is 
ordinarily  fixed  by  its  thinner  extremity  to  some  solid  object. 
In  Vaginicola  (Fig.  11,  a),  again,  we  have  an  animalcule 
closely  related  to  Stentor,  but  having  the  body  protected  by  a 
horny  or  membranous  sheath. 

All  the  Infusoria  we  have  been  hitherto  considering  belong  to  a  section 
of  the  class  in  which  the  surface  is  furnished  with  more  or  less  numerous 
cilia.  There  are  other  forms,  however,  in  which  there  are  no  cilia,  but  the 
body  is  furnished  with  a  number  of  radiating  filamentous  tubes,  the  extremi- 
ties of  which  form  little  sucking-disks.  Finally,  there  is  another  section  in 
which  the  organs  of  locomotion  are  in  the  form  of  long,  contractile  filaments, 
termed  "  flagella,"  which  may  be  combined  with  cilia,  or  may  be  the  only 
locomotive  organs  present.  In  accordance  with  these  differences,  the  Infu- 
soria are  divided  into  the  three  orders  of  the  Ciliata,  Suctoria,  and  Flagel- 
lata,  of  which  the  ciliated  forms  are  by  far  the  most  numerous  and  most  im- 
portant. 

DISTRIBUTION  OF  INFUSORIA  IN  SPACE. — As  regards  the  distribution  of 
Infusoria  in  space,  there  is  little  to  say,  except  that  they  are  of  universal 
occurrence  in  fresh  water  over  the  whole  globe,  and  that  they  occur  also  in 
the  sea.  In  fact,  the  only  conditions  which  appear  to  be  necessary  for  their 
existence  are  a  certain  quantity  of  water  holding  organic  matter  in  solution. 
Wherever  these  conditions  are  fulfilled.  Infusoria  are  certain  to  make  their 
appearance.  The  attached  forms  of  Infusoria,  however  (such  as  Vorticella, 
Epistylis,  Stentor,  and  others),  do  not  appear  to  be  ever  developed  in  artifi- 
cial infusions,  and  they  are  to  be  sought  for  on  the  stems  of  water-plants, 
and  in  other  similar  localities.  It  seems  hardly  necessary  to  remark  that, 
as  before  defined,  the  occurrence  of  fossil  Infusoria  is  not  to  be  looked  for, 
as  they  possess  no  hard  structures  which  are  capable  of  permanent  preser- 
vation. It  is  only  to  be  added  in  this  connection  that,  if  the  animalcule 
known  as  Noctiluca  be  rightly  referred  to  this  class,  the  Infusoria  take  a 
very  decided  share  in  producing  the  diffused  phosphorescence  or  luminosity 
of  the  sea,  which  is  occasionally  such  a  beautiful  spectacle  even  in  our  own 
climate. 


SUB-KINGDOM  IL—C(ELENTERATA. 
CHAPTER  IV. 

1.  CHAEACTEES  or  THE  SUB-KINGDOM.     2.  DIVISIONS. 

3.  GENEEAL  CHAEACTEES  OF  THE  HYDEOZOA. 

4.  EXPLANATION  OF  TECHNICAL  TEEMS. 

IN  the  sub-kingdom  Ccelenterata  are  included  the  sea- 
anemones,  corals,  sea-jellies,  sea-firs,  and  other  allied  animals, 
and  the  whole  division  may  be  looked  upon  as  forming  the 
most  typical  section  of  the  animals  formerly  called  by  Cuvier 
Radiata.  In  addition,  however,  to  the  above-mentioned  ani- 
mals, Cuvier  included  in  his  Radiata  all  the  members  of  the 
modern  sub-kingdom  Protozoa,  together  with  the  sea-mats  or 
lowest  class  of  the  Mollusca,  and  the  sea-urchins,  star-fishes, 
wheel-animalcules,  internal  parasites,  and  others  which  are 
now  placed  in  a  separate  sub-kingdom  by  themselves  (Annu- 
loida).  The  old  Radiata,  therefore,  was  an  extremely  hetero- 
geneous assemblage,  and  there  is  no  advantage  to  be  derived 
from  its  employment  even  in  works  such  as  this  present.  The 
division  Ccelenterata,  or  "  hollow-entrailed "  animals  (Gr. 
Jcoilos,  hollow;  and  enter  on,  intestine),  includes  all  those  radi- 
ate animals  which  are  more  or  less  closely  allied  to  the  sea- 
anemones  on  the  one  hand,  and  to  the  sea-firs  on  the  other. 
Most  of  the  Ccelenterata  come  under  the  conveniently  loose 
term  of  "  zoophytes,"  or  plant-animals,  from  the  external  re- 
semblance which  many  of  them  show  to  plants. 

The  Ccelenterata  may  be  defined  as  animals  whose  aliment- 
ary canal  communicates  freely  with  the  general  cavity  of 
the  body  ^somatic  cavity").  The  body  is  essentially  com- 
posed of  two  layers  or  membranes,  an  outer  layer  or  "  ecto- 
derm," and  an  inner  layer  or  "  endoderm"  No  circulatory 
organs  exist,  and  in  most  there  are  no  traces  of  a  nervous 


CCELENTERATA. 


51 


system.  Peculiar  stinging  organs,  or  "  thread-cells"  are 
usually  if  not  always  present,  and  in  most  cases  there  is  a 
radiate  or  star-like  arrangement  of  the  organs,  which  is 
especially  perceptible  in  the  tentacles,  which  are  in  most  in- 
stances placed  round  the  mouth.  Distinct  reproductive  organs 
exist  in  all. 

The  leading  feature  which  distinguishes  the  Ccelenterata, 
and  the  one  from  which  the  name  of  the  sub-kingdom  is  de- 
rived, is  the  peculiar  arrangement  of  the  digestive  system.  In 
the  Protozoa,  as  we  have  seen,  a  mouth  is  only  very  rarely 
present,  and  in  no  case  is  there  any  definite  internal  cavity 
bounded  by  the  walls  of  the  body,  to  which  the  name  of 
"  body-cavity  "  or  "  somatic  cavity  "  could  be  properly  applied. 
In  most  of  the  higher  animals,  on  the  other  hand,  not  only  is 
a  permanent  mouth  present,  but  the  walls  of  the  body  enclose 
a  distinct  and  permanent  chamber  or  body-cavity.  Further, 
in  most  cases  the  mouth  opens  into  an  alimentary  or  digestive 
tube,  which  is  always  distinct  from  the  body-cavity,  and  never 
opens  into  it,  usually  passing  through  it  to  open  on  the  sur- 
face by  another  distinct  aperture  (the  anus).  In  most  cases, 
therefore,  the  alimentary  canal  is  a  tube  which  communicates 
with  the  outer  world  by  two  apertures — a  mouth  and  an 
anus — but  which  simply  passes  through  the  body-cavity  with- 
out in  any  way  communicating  with  it.  In  the  Coelenterata 
(Fig.  12)  the  condition  of  parts  is  intermediate  in  its  arrange- 


FIG.  12.— Diagrammatic  vertical  section  of  a  Sea-anemone  (Actinia),  a  Stomach;  5  Mesen- 
tery ;  c  Convoluted  cord  or  '  craspedum ; "  d  Tentacle.  The  dark  line  indicates  the 
u  ectoderm,"  the  fine  line  and  clear  space  adjacent  mark  the  "  endoderm." 

ment.     There  is  a  distinct  and  permanent  mouth,  and  there 
is  a  distinct  and  permanent  body-cavity,  but  the  mouth  opens 


52  INVERTEBRATE  ANIMALS. 

into,  and  thus  communicates  freely  with,  the  body-cavity.  In 
some  cases  the  mouth  opens  straight  into  the  general  body- 
cavity,  which  then  serves  as  a  digestive  cavity  as  well  (Fig. 
13,  a).  In  other  cases  there  intervenes  between  the  mouth 
and  the  body -cavity  a  short  alimentary  tube,  which  communi- 
cates externally  with  the  outer  world  through  the  mouth,  and 
opens  below  by  a  wide  aperture  into  the  general  cavity  of  the 
body.  In  no  case  is  there  a  distinct  intestinal  tube  which 
runs  through  the  body-cavity  and  opens  on  the  surface  by  a 
mouth  at  one  end  and  an  excretory  aperture  or  anus  at  the 
other.  Another  leading  character  of  the  Coelenterata  is  the 
composition  of  the  body  out  of  two  fundamental  membranes 
(Fig.  12),  which  are  usually  of  a  very  simple  structure,  but 
which  may  be  more  or  less  complicated  by  the  development 
of  muscular  fibres  and  other  tissues.  The  outer  of  these 
layers  or  membranes  is  known  as  the  "ectoderm,"  and  it 
forms  the  whole  of  the  outer  surface  of  the  body,  terminating 
at  the  margins  of  the  mouth.  The  inner  layer  is  known  as 
the  "  endoderm,"  and  it  lines  the  whole  of  the  interior  of  the 
body,  being  prolonged  into  the  tubular  tentacles  round  the 
mouth.  Both  of  these  membranes,  but  especially  the  endoderm, 
are  usually  more  or  less  richly  furnished  with  vibrating  cilia. 
The  peculiar  microscopic  organs  called  "  thread-cells,"  or  "  net- 
tle-cells," which  communicate  to  many  of  the  Coelenterata 
(such  as  the  sea-jellies)  their  peculiar  power  of  stinging,  are 
structures  found  in  the  integument  of  almost  all  the  mem- 
bers of  this  sub-kingdom,  and  sometimes  in  internal  parts  as 
well.  They  are  very  beautiful  objects  of  microscopical  ex- 
amination, and  differ  very  considerably  in  the  details  of  their 
structure.  They  are,  however,  in  most  respects  essentially 
the  same  as  in  the  common  Hydra  or  fresh-water  polype,  in 
which  the  thread-cells  (Fig.  13,  d)  are  "  oval  elastic  sacs,  con- 
taining a  long,  coiled  filament,  barbed  at  its  base  and  serrated 
along  its  edges.  When  fully  developed  the  sacs  are  tensely 
filled  with  fluid,  and  the  slightest  touch  is  sufficient  to  cause 
the  retroversion  of  the  filament,  which  then  projects  beyond 
the  sac  for  a  distance,  which  is  not  uncommonly  equal  to  many 
times  the  length  of  the  latter"  (Huxley). 

In  accordance  with  the  above-mentioned  differences  in  the 
arrangement  of  the  digestive  system,  the  Coelenterata  are 
divided  into  two  great  classes,  termed  respectively  the  Hy- 
drozoa  and  the  Actinozoa.  In  the  Hydrozoa^  there  is  no 
body-cavity  distinct  from  the  digestive  cavity — or,  in  other 
words,  the  body-cavity  is  the  digestive  cavity.  In  the  A.cti~ 


CCELENTERATA.  53 

nozoa,  on  the  other  hand,  there  is  a  distinct  digestive  cavity, 
but  this  opens  directly  into  the  general  body-cavity,  so  that 
the  two  form  distinct  but  freely-communicating  divisions  of 
the  same  chamber. 

CLASS  I. — HYDEOZOA. 

The  Hydrozoa  are  defined  as  Ccelenterata  in  which  the 
walls  of  the  digestive  sac  are  not  separated  from  those  of  the 
general  cavity  of  the  body,  the  two  coinciding  with  one  an- 
other. The  reproductive  organs  are  external,  in  the  form  of 
outward  processes  of  the  body-wall  (Fig.  13,  a,  b). 

The  Hydrozoa  are  all  aquatic  in  their  habits,  and,  with 
the  exception  of  two  genera,  all  are  inhabitants  of  salt  water. 
The  class  includes  both  simple  and  composite  organisms,  of 
which  the  most  familiar  are  the  sea-firs  and  their  allies  (Hy- 
dro id  zoophytes),  the  fresh- water  polype  or  Hydra,  the  sea- 
jellies  (Medusae),  and  the  Portuguese  man-of-war  (Physalia). 
Owing  to  the  extremely  complicated  nature  of  many  of  the 
Hydrozoa,  it  appears  advisable  to  preface  their  description 
by  an  explanation  of  some  of  the  more  important  terms  which 
are  employed  in  connection  with  various  members  of  the 
class. 

GENEEAL  TEEMIXOLOGY  OF  THE  HYDEOZOA. 

Individual. — In  order  to  understand  fully  the  meaning 
which  is  attached  to  the  term  "  individual "  in  zoological  lan- 
guage, it  is  necessary  to  glance  briefly  at  the  general  features 
of  reproduction  as  displayed  in  different  sections  of  the  ani- 
mal kingdom.  Reproduction  is  the  process  by  means  of  which 
new  individuals  are  produced  and  the  perpetuation  of  the 
species  insured.  This  end  may  be  attained  in  various  ways, 
but  these  all  come  under  the  two  head's  of  "  sexual "  and 
"  non-sexual "  reproduction.  In  sexual  reproduction,  by  which 
alone  can  fresh  beings  be  produced  among  the  higher  ani- 
mals, the  essential  element  of  the  process  consists  in  the 
formation  of  two  distinct  structures,  a  germ-cell  or  ovum,  and 
a  sperm-cell  or  spermatozoid.  By  the  union  of  these  distinct 
reproductive  elements  fresh  beings  can  be  produced.  As  a 
general  rule,  the  germ-cell  is  produced  by  one  individual 
(female),  and  the  sperm-cell  by  another  (male) ;  but  among 
the  lower  animals  it  is  not  uncommon  for  the  same  individual 
to  produce  both  of  these  elements,  in  which  case  the  indi- 
vidual is  said  to  be  "hermaphrodite."  Among  the  lower 
animals,  however,  fresh  beings  may  be  produced  without  the 


64  INVERTEBRATE  ANIMALS. 

contact  of  a  sperm-cell  and  an  ovum — that  is  to  say,  without 
any  genuine  act  of  reproduction.  The  processes  by  which  this 
can  be  effected  in  different  animals  vary  considerably,  but  they 
are  all  spoken  of  as  forms  of  "  non-sexual "  reproduction.  The 
only  varieties,  however,  of  the  process  which  require  considera- 
tion, are  those  in  which  fresh  beings  are  produced  by  what 
is  called  "  gemmation  "  or  "  fission." 

Gemmation  (Lat.  gemma,  a  bud)  consists  in  the  produc- 
tion of  a  bud  or  buds,  usually  from  the  outside,  but  sometimes 
from  the  inside,  of  an  animal ;  which  buds  become  developed 
into  more  or  less  completely  independent  beings.  The  fresh 
beings  thus  produced  by  budding  are  all  known  as  zooids,  and 
are  not  spoken  of  as  distinct  animals  for  reasons  which  will  be 
immediately  evident.  When  the  zooids  produced  by  budding 
remain  permanently  attached  to  one  another  and  to  the  parent 
organism  which  produced  them,  the  case  is  said  to  be  one  of 
"continuous"  gemmation,  and  the  ultimate  result  of  this  is 
to  produce  a  colony  or  composite  structure,  composed  of  a 
number  of  similar  and  partially  independent  beings,  all  pro- 
duced by  budding,  but  all  remaining  in  organic  connection. 
This  is  seen  very  well  in  the  sponges,  in  the  compound  Fora- 
minifera,  and  in  a  great  number  of  the  Hydrozoa.  When,  on 
the  other  hand,  the  zooids  produced  by  budding  become  finally 
detached  from  the  parent  organism,  we  have  a  case  of  what  is 
called  "  discontinuous  "  gemmation.  In  this  case,  the  detached 
zooids  become  completely  independent  beings ;  and  they  are 
often  wholly  unlike  the  original  zooid  in  structure  and  in 
habits,  so  much  so  that  they  have  in  various  cases  been  de- 
scribed as  altogether  distinct  animals.  Discontinuous  gem- 
mation is  very  well  seen  in  many  of  the  Hydrozoa,  and  in 
them  the  case  is  still  further  complicated  by  the  coexistence 
of  discontinuous  gemmation  with  the  continuous  form  of  the 
process.  Thus,  it  is  not  an  uncommon  thing  among  the 
Hydrozoa  to  find  a  composite  organism  or  colony  produced 
from  a  primordial  zooid  by  continuous  gemmation,  and  hav- 
ing at  the  same  time  the  power  of  giving  rise  to  detached  and 
completely  independent  beings  by  a  process  of  discontinuous 
gemmation. 

In  what  is  called  "fission"  (Lat.  findo,  I  cleave),  exactly 
the  same  results  are  attained  as  in  gemmation,  but  in  a 
slightly  different  manner.  In  gemmation  the  new  beings  are 
produced  by  means  of  buds  thrown  out  by  a  primitive  zo5id. 
In  fission  the  new  beings  are  produced  by  a  cleavage  or 
division  of  a  primitive  zooid  into  two  or  more  parts,  each  of 


CCELENTERATA.  55 

which  becomes  finally  developed  into  a  new  and  more  or  less 
completely  independent  being.  In  fission,  as  in  gemmation, 
the  new  beings  or  zoo'ids  may  remain  permanently  in  con- 
nection with  one  another,  when  the  process  is  a  continuous 
one,  and  a  composite  organism  is  produced,  as  in  many  corals. 
Or,  in  other  cases,  the  new  zoo'ids  produced  by  fission  are  de- 
tached to  lead  an  independent  existence,  as  in  some  of  the 
Hydrozoa,  the  process  thus  becoming  a  discontinuous  one. 

We  are  now  able  to  understand  what  is  meant,  in  strict 
zoological  language,  by  the  term  "  individual,"  as  applied  to 
animals.  Zoologically  speaking,  an  individual  is  defined  as 
"equal  to  the  total  result  of  the  development  of  a  single 
ovum"  In  the  higher  animals  there  is  no  sort  of  difficulty 
about  this,  for  each  ovum  gives  rise  to  no  more  than  one 
single  animal,  which  cannot  produce  fresh  beings  in  any  other 
way  than  by  producing  another  ovum.  In  this  case,  there- 
fore, each  animal  is  an  individual.  In  the  lower  animals, 
however,  the  being  produced  by  an  ovum  has  often  the  power 
of  giving  rise  to  fresh  beings  by  a  process  of  gemmation  or 
fission,  and  these  beings  may  either  remain  attached  to  one 
another  so  as  to  form  a  colony,  or  may  become  detached  to 
lead  independent  lives.  In  either  case,  the  term  "  individual " 
can  only  be  properly  applied  to  the  whole  assemblage  of  be- 
ings produced  in  this  way,  however  much  they  may  differ 
from  one  another  in  appearance,  structure,  or  mode  of  life. 
In  these  cases,  therefore,  the  individual  may  be,  firstly,  a 
single  independent  being — as,  for  instance,  an  Amoeba,  or  an 
Infusorian  such  as  Paramoecium  •  secondly,  a  colony  or  com- 
posite organism  composed  of  a  number  of  more  or  less  nearly 
similar  beings  or  zooids,  produced  by  budding  from  a  primi- 
tive zooid — as,  for  instance,  a  sponge,  or  such  an  Infusorian 
as  Epistylis  ;  and  thirdly,  an  assemblage*  of  zo5ids  produced 
by  budding  or  fission  from  a  primitive  being,  but  not  neces- 
sarily remaining  connected  with  one  another  or  exhibiting 
any  common  features  of  likeness,  as  we  shall  see  is  the 
case  in  many  of  the  Hydrozoa.  Lastly,  cases  may  occur  in 
which  the  individual  consists  partly  of  similar  zo5ids  which 
remain  permanently  connected  with  one  another,  and  partly 
of  dissimilar  zo5ids  which  are  detached-to  lead  an  independent 
life,  all  alike  being  the  result  of  the  development  of  a  single 
ovum. 

Zooid  (Gr.  zodn,  animal;  eidos,  form). — The  term  "zooid" 
is  indifferently  applied  to  all  the  more  or  less  completely  in- 
dependent beings  which  are  produced  by  budding,  or  by 


56  INVERTEBRATE  ANIMALS. 

cleavage  from  a  primitive  organism.  It  does  not  matter, 
therefore,  for  the  purposes  of  this  definition,  whether  these 
beings  remain  permanently  attached  to  the  original  organism, 
or  whether  they  are  finally  separated  to  enjoy  an  independent 
existence. 

Hydrosoma  (Gr.  liudra,  a  water-serpent;  soma,  body). — 
The  term  "  hydrosoma  "  is  one  which  is  very  conveniently  ap- 
plied to  the  entire  organism  in  any  Hydrozoon,  whether  this 
be  simple,  or  whether  it  be  composite  and  made  up  of  a  num- 
ber of  connected  zoOids. 

Potypite. — That  portion  of  any  Hydrozoon  which  is  con- 
cerned with  the  process  of  digestion,  or,  in  other  words,  the 
"alimentary  region,"  is  termed  the  "polypite" — the  more 
generally  current  term  of  "  polype  "  being  now  restricted  in 
meaning  to  the  same  region  in  the  higher  Coelenterata  (Ac- 
finozoa).  In  such  of  the  Hydrozoa  as  the  fresh-water  polype 
or  Hydra,  in  which  the  hydrosoma  is  simple,  the  whole  or- 
ganism is  termed  a  polypite ;  but  the  term  is  more  generally 
employed  to  indicate  the  nutritive  zooids  of  any  compound 
Hydrozoon. 

Ccenosarc. — The  term  "  coenosarc  "  (Gr.  Jcoinos,  common ; 
sarx,  flesh)  is  employed  to  designate  the  common  trunk  or 
flesh  by  which  the  separate  polypites  of  any  compound  Hy- 
drozoon are  united  into  a  single  organic  whole. 

Polypary. — The  term  "  polypary  "  or  "  polypidom  "  is  ap- 
plied to  the  horny  or  chitinous  outer  covering  or  envelope 
with  which  many  of  the  Hydrozoa  are  furnished.  These  terms 
have  also  been  not  uncommonly  employed  to  designate  the 
very  similar  structures  produced  by  the  much  more  highly  or- 
ganized sea-mats  and  their  allies  (Polyzoa),  but  it  is  better  to 
restrict  their  use  entirely  to  the  Hydrozoa. 


CHAPTER  Y. 
DIVISIONS  OP  THE  HYDEOZOA. 

THE  Hydrozoa  are  divided  into  four  great  divisions,  each 
of  which  requires  some  notice,  as  presenting  points  of  special 
interest.  These  divisions  or  sub-classes  are  known  by  the  names 
of  Hydroida,  Siphonophora,  Discophora,  and  Lucernarida. 

SUB-CLASS   HYDROIDA. 

This  sub-class  comprises  all  the  sea-firs  and  their  allies, 
commonly  known  to  naturalists  as  the  "  Hydroid  zoophytes," 
from  their  resemblance  to  the  fresh-water  polype  (Hydra), 
which  is  also  a  member  of  this  division.  The  Hydroida  are 
defined  by  the  fact  that  they  consist  of  an  alimentary  region 
or  " polypite"  which  is  furnished  with  a  mouth  and  prehensile 
tentacles  at  one  end,  and  with  an  adherent  disk  at  its  other 
extremity.  In  some  few  cases  the  hydrosoma  consists  of  but 
one  such  polypite  (as  in  the  Hydrida  and  some  of  the  Co- 
rynida)  •  but  generally  the  hydrosoma  is  composed  of  a 
greater  or  less  number  of  similar  polypites  all  united  by  a 
ccenosarc  or  common  trunk  (as  in  the  majority  of  the  Corynida, 
and  in  the  Sertularida  and  Campanularida).  In  the  great 
majority  of  cases,  also,  the  hydrosoma  is  nqt  unattached,  but 
is  fixed  to  some  solid  object  by  one  extremity.  The  Hydroid 
zoophytes  exhibit  three  principal  types  of  structure,  which 
constitute  so  many  orders. 

ORDER  I.  HYDRIDA. — In  the  first  order  we  have  only  the 
well-known  fresh-water  polypes  or  Hydrce,  of  which  we  may 
take  the  common  green  Hydra  (H.  viridis)  as  the  type.  This 
singular  little  creature  may  be  found  with  a  little  trouble  in 
most  of  our  streams  and  pools,  and  it  is  quite  visible  to  the 
naked  eye,  though  it  can  only  be  satisfactorily  examined  by 


68 


INVERTEBRATE  ANIMALS. 


the  help  of  the  microscope.  When  uncontracted,  the  body  of 
the  Hydra  is  in  the  form  of  a  cylindrical  tube  (Fig.  13,  a,  5), 
composed  of  the  two  fundamental  layers,  the  ectoderm  and 
endoderm,  of  which  the  former  contains  many  thread-cells, 
and  is  likewise  furnished  with  numerous  green  granules,  stated 
to  be  identical  with  "  chlorophyll,"  or  the  green  coloring- 
matter  of  plants.  At  the  base  of  the  cylindrical  body  is  a 
kind  of  disk-shaped  sucker,  by  means  of  which  the  animal  can 
attach  itself  at  will  to  any  foreign  body.  Its  favorite  position 
appears  to  be  that  of  hanging  head-downward,  suspended 
from  the  stem  of  some  water-plant.  It  is  not,  however,  per- 
manently fixed,  but  it  can  detach  itself  and  change  its  place 
at  will.  At  the  opposite  extremity  of  the  body  is  placed  the 
aperture  of  the  mouth,  surrounded  by  a  circle  of  from  five  to 
fifteen  small  tubular  filaments,  which  are  termed  the  "  tenta- 


FIG.  13.— Morphology  of  Hydrozoa.  a  Diagrammatic  section  of  Hydra :  the  dark  line  is 
the  ectoderm,  the  fine  line  and  clear  space  adjacent  indicate  the  endoderm ;  6  Hydra 
viridis,  showing  a  single  ovum  contained  in  the  body-wall  near  the  lower  extremity, 
and  two  conical  elevations  containing  sperm-cells  near  the  bases  of  the  tentacles. 
c  Hydra  vulgaris,  with  an  undetached  bud — enlarged ;  d  Thread-cell  of  the  Hydra, 
greatly  magnified. 

cles  "  (Fig.  13,  b).  Each  tentacle  consists  of  a  tubular  prolon- 
gation of  both  ectoderm  and  endoderm,  and  encloses  a  canal 
which  opens  at  its  base  into  the  general  cavity  of  the  body. 
The  ectoderm  of  the  tentacles  is  richly  furnished  with  thread- 
cells,  and  they  are  also  well  supplied  with  muscular  fibres. 
They  exhibit  the  most  extraordinary  contractility,  being  capa- 
ble of  retraction  till  they  appear  as  nothing  more  than  so 
many  little  warts  or  tubercles,  and  of  being  extended  to  a 


DIVISIONS  OF  THE  HYDROZOA.  59 

length  which  is  in  some  species  many  times  longer  than  the 
body  itself.  (In  Hydra  fusca  the  tentacles  can  be  protruded 
to  a  length  of  more  than  eight  inches.)  The  tentacles  are  the 
organs  by  means  of  which  the  Hydra  obtains  its  food,  con- 
sisting chiefly  of  minute  aquatic  organisms,  such  as  small 
worms,  insects,  Crustacea  and  Eotifera.  These  are  seized 
by  the  tentacles  and  gradually  drawn  into  the  mouth  ;  but  in 
addition  to  this  merely  mechanical  action,  the  tentacles  ap- 
pear to  exercise  a  benumbing  or  even  fatal  influence  upon  the 
animals  grasped  by  them — this  being  apparently  due  to  the 
thread-cells  with  which  they  are  furnished.  The  mouth  in 
the  Hydra  opens  directly  into  a  capacious  cylindrical  cavity, 
which  is  excavated  along  the  whole  length  of  the  body,  and 
which  is  both  the  body-cavity  and  the  stomach  in  one.  This 
cavity  (Fig.  13,  a,  b)  is  filled  with  water  derived  from  the 
exterior,  and  also  with  the  nutritive  particles  derived  from 
the  food.  Indigestible  fragments  appear  to  be  rejected  by 
the  mouth,  though  an  anal  aperture  has  been  asserted  to  be 
present.  There  are  no  internal  organs  of  any  kind.  Physio- 
logically, therefore,  the  Hydra  presents  little  advance  upon 
the  higher  Protozoa,  such  as  the  Infusoria.  There  is  a  per- 
manent mouth,  surrounded  by  permanent  and  special  organs 
adapted  for  the  seizure  of  food.  There  is  also  a  permanent 
internal  cavity  for  the  reception  and  digestion  of  the  food, 
but  this  is  not  shut  off  from  the  general  cavity  of  the  body. 
There  is  no  organ  for  the  propulsion  of  the  nutritive  fluid 
through  the  body,  no  nervous  system  or  organs  of  sense,  and 
no  special  respiratory  or  excretory  organs.  Another  and 
striking  proof  of  the  essentially  low  position  of  the  Hydra  in 
the  "animal  scale  is  to  be  found  in  its  extraordinary  capacity 
of  resisting  mutilation,  or,  in  fact,  mechanical  injury  of  any 
kind  short  of  absolute  annihilation.  The  briefest  illustration 
of  this  fact  is  all  that  can  here  be  given,  but  with  that  the 
name  of  Trembley  of  Geneva  must  be  associated.  This  well- 
known  observer,  in  a  long  series  of  experiments,  most  of 
which  have  been  successfully  repeated  by  subsequent  nat- 
uralists, discovered  that  the  Hydra  could  be  mechanically 
divided  with  a  knife  into  any  number  of  fragments,  with  the 
sole  result  that  each  and  all  of  these  possessed  the  power 
of  developing  themselves  into  fresh  and  independent  polypites. 
Further,  the  animal  could  even  be  turned  inside  out,  with 
a  necessary  transposition  of  the  ectoderm  and  endoderm, 
without  any  apparent  inconvenience  or  interference  with  its 
health. 


60  INVERTEBRATE  ANIMALS. 

Reproduction  in  the  Hydra  is  effected  non-sexually  by 
gemmation,  and  sexually  by  the  production  of  ova  and  sperm- 
cells  ;  the  former  process  being  followed  in  summer  and  the 
latter  in  autumn,  few  individuals  appearing  to  survive  the 
winter.  In  the  first  or  non-sexual  method,  the  Hydra  throws 
out  one  or  more  buds,  usually  from  near  the  fixed  extremity 
(Fig.  13,  c).  These  buds  at  first  consist  simply  of  a  tubular 
prolongation  of  the  ectoderm  and  endoderm,  enclosing  a 
cavity  which  communicates  with  the  general  cavity  of  the 
body.  A  new  mouth  and  tentacles  are  soon  developed  at  the 
free  end  of  this  bud,  and  after  a  longer  or  shorter  period  the 
new  If ydr a,  thus  produced,  is  detached  to  lead  an  independent 
life.  Each  Hydra  can  produce  many  such  buds  during  the 
summer  season,  and  the  liberated  buds  can  also  repeat  the 
same  process,  so  that  in  this  way  reproduction  is  rapidly 
carried  on.  In  the  second  or  sexual  method  of  reproduction, 
ova  and  sperm-cells  are  produced  toward  the  winter  in  ex- 
ternal processes  of  the  body-wall.  The  spermatozoa  are  de- 
veloped in  little  conical  elevations,  which  are  produced  near 
the  bases  of  the  tentacles ;  and  the  ova  are  formed  in  much 
larger  elevations,  of  which  there  is  ordinarily  but  one,  placed 
nearer  to  the  fixed  extremity  of  the  animal  (Fig.  13,  b).  When 
mature,  the  ovum  is  fertilized  by  the  sperm-cells,  both  being 
set  free  into  the  water  by  the  rupture  of  the  body-wall.  The 
embryo  Hydra  is  at  first  covered  with  vibrating  cilia,  and 
swims  freely  about,  until  it  meets  with  a  suitable  locality. 
It  then  fixes  itself  by  one  extremity,  the  cilia  drop  off,  and 
a  mouth  and  tentacles  are  developed  at  the  free  end  of  the 
body. 

OKDER  II.  CORYNIDA. — In  the  second  order  of  the  Hydroid 
zoophytes,  known  as  the  Corynida  or  Tubularida,  \ve  have  a 
number  of  organisms  which  in  their  essential  structure  are 
closely  related  to  the  Hydra,  but  which  differ  considerably 
in  the  nature  of  the  reproductive  process.  All  of  them  are 
marine,  with  the  single  exception  of  the  genus  Cordylophora, 
which  inhabits  fresh  water.  Some  of  the  members  of  the 
order  are  simple,  consisting  of  no  more  than  a  single  polypite. 
In  these  cases  there  is  an  exceedingly  close  approach  to  the 
structure  of  the  common  Hydra,  but  the  polypite  is  per- 
manently fixed  without  the  power  of  voluntarily  changing  its 
place,  while  the  reproductive  process  is  considerably  different. 
In  the  majority  of  the  Corynida,  however,  the  hydrosoma  is 
compound,  consisting  of  a  greater  or  less  number  of  separate 


DIVISIONS  OF  THE  HYDROZOA. 


61 


polypites  or  zoo'ids,  all  connected  with  one  another  by  a  com- 
mon flesh  or  ccenosarc,  and  all  forming  parts  of  a  plant-like 
rooted  colony.  In  some  of  the  Corynida  the  polypites  are 
naked,  but  in  most  cases  the  ccenosarc  is  protected  by  a 
horny-looking  chitinous  *  envelope  or  "  polypary,"  as  in 
Tubularia  indivisa  (Fig.  14).  In  no  case,  however,  is  this 
horny  covering  so  prolonged  as  to 
form  little  cups  in  which  each  poly- 
pite  is  contained.  It  always  stops 
short  at  the  bases  of  the  polypites, 
and  in  this  way  the  Corynida  can  al- 
ways be  distinguished  from  their  near 
allies,  the  sea-firs  (Sertularida). 

As  a  good  example  of  the  Cory- 
nida, the  common  pipe  -  coralline 
(Tubularia  indivisa)  may  be  taken. 
In  this  animal  (Fig.  14)  we  have  a 
gregarious  zoophyte  consisting  of 
numerous  clustered  horny  tubes,  fixed 
by  their  bases  to  shells  or  stones,  and 
inhabiting  most  seas.  The  tubes  are 
usually  unbranched,  though  often  con- 
siderably interwoven  together.  Each 
tube  is  filled  with  a  soft,  semi-fluid, 
reddish  ccenosarc,  and  gives  exit  at 
its  free  extremity  to  a  single  poly- 
pite.  The  polypites  are  bright  red  in 
color,  and  are  not  retractile  within 
their  tubes,  the  horny  polypary  ex- 
tending only  to  their  bases.  The 
polypites  are  somewhat  conical  in 
shape,  the  mouth  being  placed  at  the 
apex  of  the  cone,  and  they  are  furnished  with  two  sets  of  ten- 
tacles. One  set  consists  of  numerous  short  tentacles  placed 
directly  round  the  mouth,  the  other  is  composed  of  from 
thirty  to  forty  tentacula  of  much  greater  length  arising  from 
the  polypite  about  its  middle  or  near  its  base.  Near  the  in- 
sertion of  these  tentacles  the  generative  buds  are  produced  at 
proper  seasons.  In  Eudendrium  (the  branched  pipe-coral- 
line) the  essential  structure  is  much  the  same  as  dn  Tubularia, 
but  the  hydrosoma  is  now  truly  compound,  consisting  of  a 
number  of  non-retractile  reddish  polypites,  united  by  a  cceno- 

*  ChUine  is  a  sxibstance  which  is  nearly  allied  to  horn,  but  is  distinguished  from  it  by 
the  fact  that  it  is  not  soluble  in  caustic  potash. 


FIG.  14. — Fragment  of  Tiibularia 
indivisa,  natural  size. 


62 


INVERTEBRATE  ANIMALS. 


sarc,  which  is  furnished  with  a  horny  polypary,  the  whole 
colony  assuming  a  singularly  close  resemblance  to  a  plant.  In 
Cordylophora — the  only  fresh-water  member  of  the  order — we 
find  also  a  branched  composite  hydrosoma  carrying  numerous 
polypites,  and  having  the  ccenosarc  defended  by  a  horny  sheath 
(Fig.  15,  #,  b).  In  Coryomorpha,  finally,  we  have  a  type  of  the 


FIG.  15. — a  Fragment  of  Cordylophora  lacwtris,  slightly  enlarged;  5  Fragment  of  th* 
same,  considerably  enlarged,  showing  a  polypite  and  three  gonophores  in  different 
stages  of  growth ;  e  Portion  of  Syncoryne  /Sarsii,  with  medusifbrm  zooids  budding  be- 
tween the  tentacles. 

Corynida,  in  which  the  hydrosoma  consists  of  no  more  than  a 
single  polypite,  and  there  is  no  polypary.  It  is  about  four 
inches  in  length,  and  is  fixed  by  filamentous  roots  to  the  bot- 
tom of  the  sea.  It  consists  of  a  single  whitish  polypite,  striped 
with  pink,  and  terminating  upward  in  a  pear-shaped  head, 
furnished  with  two  sets  of  tentacles,  the  shortest  of  which 
form  a  circlet  round  the  mouth. 

As  regards  the  generative  process  in  the  Corynida,  it  may 
be  as  well  to  consider  the  general  phenomena  of  reproduction 
as  carried  on  by  all  the  Hydroid  zoophytes,  the  general  char- 
acters of  the  process  being  of  a  most  remarkable  nature.  As 
has  been  already  explained,  the  individual  in  the  case  of  the 
compound  Hydrozoa  consists  of  an  aggregation  or  colony  of 
partially  independent  beings  or  zo5ids,  produced  by  gemma- 
tion or  fission  from  a  primordial  organism.  This  is  the  case 
in  all  composite  animals,  such  as  sponges,  sea-mats,  corals, 
and  many  others.  In  many  of  the  compound  Uydrozoa,  how- 
ever, the  case  becomes  still  further  complicated.  In  many  of 
these  organisms,  namely,  the  zo5ids  differ  very  much  from  one 
another  both  in  structure  and  in  function.  One  set  of  zooids 


DIVISIONS  OF  THE   HYDROZOA.  63 

is  entirely  devoted  to  the  duty  of  providing  food  for  the  col- 
ony, and  in  these  no  reproductive  organs  are  ever  developed. 
These  nutritive  zooids  are  all  like  each  other  in  form,  and  the 
whole  assemblage  of  them  has  been  appropriately  termed  the 
"trophosome"  (Allman),  from  the  Greek  trepho,!  nourish; 
and  soma,  body.  The  colony  or  trophosome  thus  formed  by 
the  nutritive  zooids  can  go  on  increasing  by  the  production 
of  fresh  zooids  for  an  almost  indefinite  period ;  but  in  all  cases 
there  ultimately  comes  a  time  when  it  becomes  necessary  to 
produce  the  essential  elements  of  reproduction  in  order  to 
secure  the  perpetuation  of  the  species.  The  nutritive  zooids, 
as  just  stated,  cannot  produce  the  ova  and  sperm-cells,  being 
destitute  of  reproductive  organs,  and  the  colony  is  therefore 
compelled  to  produce  a  second  set  of  buds,  which  have  the 
power  of  producing  the  essential  elements  of  reproduction. 
These  buds  are  collectively  called  the  "gonosome"  (Gr. 
gonos,  offspring;  and  soma,  body).  The  generative  buds 
have  the  further  peculiarity  that  not  only  can  they  produce 
the  generative  elements,  but  they  are  altogether  unlike  the 
nutritive  zooids  in  appearance.  This  difference  in  external 
appearance  and  in  structure  is  sometimes  so  great  as  to  lead 
to  a  most  remarkable  series  of  phenomena.  In  the  simplest 
form  in  which  these  generative  buds  or  "  gonophores  "  appear, 
they  have  the  form  of  mere  protuberances  of  the  ectoderm 
and  endoderm  (Fig.  16,  a),  enclosing  a  cavity  derived  from 
the  body-cavity.  In  these  buds  the  generative  elements — 
ova  and  spermatozoa — are  developed  (Fig.  15,  b).  In  other 
instances,  the  generative  buds  have  a  more  complicated  struct- 


FIG.  16.— Generative  buds  or  gonophores  of  the  Hydrozoa  diagrammatically  represented. 
a  Simple  gonophore,  consisting  merely  of  a  protuberance  of  the  ectoderm  and  endo- 
derm ;  c  Gonophore  which  has  the  structure  of  a  Medusa  (medusoid),  but  is  not  de- 
tached ;  d  Free  medusiform  gonophore. 

ure.  They  consist  now  (Fig.  16,  c)  of  a  bell-shaped  disk, 
which  is  attached  by  its  base  to  the  parent  organism,  and 
has  its  cavity  turned  outward  (see  also  Fig.  15,  c).  From 


64  INVERTEBRATE  ANIMALS. 

the  roof  of  this  disk  there  is  suspended  a  kind  of  handle, 
which  corresponds  to  the  clapper  of  the  bell,  and  is  termed 
the  "  manubrium  "  (Lat.  for  handle).  From  the  fixed  or  proxi- 
mal extremity  of  the  central  process  or  manubrium  proceed 
four  canals,  which  extend  to  the  margin  of  the  bell,  where 
they  all  open  into  a  circular  canal  surrounding  the  mouth 
of  the  bell.  This  bell-shaped  reproductive  bud  may  attain  no 
higher  development  than  this,  and  may  remain  permanently 
attached  to  the  parent  organism  from  which  it  is  produced. 
In  other  cases,  however,  a  higher  state  of  development  is 
reached  (Fig.  16,  d).  The  generative  bud  or  gonophore  be- 
comes detached  from  its  parent  colony ;  the  manubrium  or 
central  process  develops  a  mouth  at  its  free  extremity;  the 
mouth  of  the  bell  becomes  partially  closed  by  an  inward  pro- 
longation or  shelf,  called  the  "  veil ; "  and  a  series  of  ten- 
tacles are  developed  from  its  margin.  The  generative  bud, 
thus  liberated,  leads  a  wholly  independent  existence.  The 
manubrium,  having  developed  a  mouth,  assumes  the  func- 
tions of  a  true  polypite,  and  its  cavity  acts  as  a  digestive 
sac.  The  whole  organism  swims  about  freely,  and  has  the 
power  of  assimilating  food,  and  thus  of  attaining  to  a  com- 
paratively gigantic  size.  This  independent  existence,  how- 
ever, only  goes  on  till  such  time  as  the  elements  of  reproduc- 
tion can  be  produced.  The  ova  and  sperm-cells  are  developed 
in  specialized  portions  of  this  generative  bud,  and  then  it 
csases  to  exist.  The  ova,  however,  when  fertilized,  do  not 
develop  themselves  into  the  free-swimming  bell-shaped  or- 
ganisms in  which  they  were  actually  produced,  but  into  the 
plant-like,  rooted,  and  compound  zoophyte,  from  which  the 
generative  buds  were  originally  given  forth.  These  free- 
swimming  bell-shaped  reproductive  buds  or  gonophores,  as 
we  shall  see,  are  identical  structurally  with  the  smaller  forms 
of  the  so-called  sea-jellies  or  Medusae  /  and  it  is  now  known 
that  most  if  not  all  of  these  Medusae,  though  originally  de- 
scribed as  distinct  beings,  are  really  nothing  more  than  the 
free  generative  buds  of  the  fixed  Hydrozoa.  We  have  here, 
then,  an  instance  of  what  has  been  not  quite  appropriately 
called  "  alternation  of  generations."  We  have  a  compound 
fixed  animal,  in  many  respects  comparable  to  a  plant,  pro- 
ducing a  special  series  of  buds  which  are  devoted  to  the  pro- 
cess of  reproduction.  These  buds  are  cast  off  as  independent 
beings  to  lead  an  independent  life,  and  they  are  furnished 
with  the  necessary  organs  to  preserve  their  existence  till  they 
are  able  to  mature  the  reproductive  elements.  When  once 


DIVISIONS  OF  THE   HYDROZOA.  65 

able  to  consummate  this,  they  die ;  but  the  young  to  which 
they  give  origin  are  wholly  unlike  themselves.  The  young, 
namely,  instead  of  being  free-swimming  "  medusiform  "  beings, 
become  developed  into  the  fixed,  plant-like  colony  from  which 
the  generative  buds  were  originally  produced.  The  term 
"  alternation  of  generations  "  is  not  an  altogether  good  one, 
and  does  not  quite  express  the  facts  of  the  case.  There  is 
not  any  alternation  of  generations,  but  there  is  an  alternation 
of  generation  with  gemmation  or  budding.  The  only  true 
generative  act  takes  place  in  the  reproductive  zooid  or  gono- 
phore,  in  which  the  ova  and  sperm-cells  are  developed.  The 
production  of  this  gonophore  from  the  parent  organism  (tro- 
phosome)  is  a  process,  not  of  generation,  but  of  gemmation 
or  budding.  The  whole  process,  therefore,  is,  properly  speak- 
ing, not  an  "  alternation  of  generations,"  but  an  alternation 
of  generation  with  gemmation. 

To  recapitulate,  then — the  process  of  reproduction  in  the 
Hydroid  zoophytes  is  carried  on  by  means  of  reproductive 
buds  or  gonophores,  which  are  produced  at  special  seasons, 
and  in  which  the  reproductive  elements  are  developed.  These 
generative  buds  differ  a  good  deal  in  their  character,  but  three 
chief  kinds  may  be  distinguished:  1.  Simple  closed  sacs  or 
protuberances  formed  out  of  both  ectoderm  and  endoderm, 
and  having  the  special  elements  of  generation  developed  in 
their  interior.  2.  Bell-shaped  buds,  attached  to  the  parent 
colony  by  their  bases,  and  having  a  central  process  or  manu- 
brium,  which  is  furnished  with  a  mouth  and  central  cavity, 
from  which  there  is  given  off  a  system  of  canals  to  ramify  in 
the  substance  of  the  disk.  The  reproductive  elements  are 
developed  either  in  the  walls  of  these  canals  or  between  the 
ectoderm  and  endoderm  of  the  manubrium.  From  the  resem- 
blance of  these  buds  in  anatomical  structure  to  the  sO'Called 
sea-jellies  or  Medusae,  they  are  usually  spoken  of  as  "  medusi- 
form gonophores,"  or  simply  as  u  medusoids."  In  this  form, 
however,  though  highly  organized,  the  buds  never  become  de- 
tached from  the  parent  colony.  3.  Buds  which  become  de- 
veloped into  bell-shaped  medusiform  bodies  exactly  similar  in 
structure  to  the  last,  but  detached  to  lead  an  independent  ex- 
istence. These  free-swimming  medusiform  gonophores  are 
anatomically  indistinguishable  from  ordinary  Medusce  /  and  it 
is  now  known  that  most,  if  not  all,  of  the  so-called  "  naked- 
eyed  "  Medusae,  are  really  the  detached  generative  buds  of 
other  orders  of  Hydrozoa.  The  special  elements  of  reproduc- 
tion are  developed  in  these  detached  buds,  but  the  resulting 


66  INVERTEBRATE  ANIMALS. 

embryos  are  not  developed  into  Medusae,  such  as  produced 
the  ova  and  sperm-cells,  but  straightway  grow  up  into  the 
plant-like,  sexless  colony,  from  which  the  medusiform  gono- 
phores  were  originally  budded  forth.  In  these  cases,  there- 
fore, the  individual  Hydroid  consists  of  a  fixed,  rooted  colony 
or  trophosome,  producing  fresh  zooids  by  a  process  of  budding, 
but  incapable  of  producing  the  essential  elements  of  reproduc- 
tion, together  with  a  free  and  independent  series  of  generative 
buds,  or  gonosome,  in  which  the  elements  of  reproduction  are 
developed. 

OEDER  III.  SEKTULAEIDA. — In  this  order  of  the  Hydroida 
we  have  the  most  familiar  and  best  known  of  all  our  zoophytes 
— namely,  the  sea-firs  and  their  allies.  The  horny,  plant-like 
polyparies  of  the  Sertularida  are  familiar  to  every  visitor  at 
the  sea-side,  and  by  those  unacquainted  with  their  true 
nature  they  are  almost  universally  set  down  as  sea-weeds. 
The  Sertularida  are  very  closely  allied  to  the  compound  forms 
of  the  Cwynida,  resembling  them  in  being  rooted,  plant- 
like  colonies,  composed  of  a  number  of  similar  polypites  or 
zooids,  produced  by  budding  from  a  primitive  zooid.  As  in 
the  Tubularians  among  the  Corynida,  the  whole  ccenosarc  is 
enveloped  in  a  horny  or  chitinous  envelope  or  polypary 
(Fig.  17,  a),  and  this  is  the  structure  which  is  most  familiarly 
known  to  sea-side  observers.  The  Sertularida,  however,  are 
distinguished  from  the  Corynida  by  two  points:  Firstly, 
none  of  the  Sertularida  are  simple,  but  are  all  compound,  con- 
sisting of  more  or  less  numerous  polypites,  united  by  a 
branched  ccenosarc.  Secondly,  the  polypary  of  the  Sertularida 
differs  from  that  of  the  Corynida  in  not  simply  reaching  to 
the  bases  of  the  polypites,  but  in  being  prolonged  to  form  a 
number  of  little  cups  or  "  hydrothecae  "  (Fig.  17,  a,  b)  within 
which  the  polypites  are  lodged.  Each  polypite  has  a  cup  of 
its  own,  within  which  it  can  entirely  withdraw,  and  from 
which  it  can  protrude  its  free  extremity. 

The  polypites  of  the  Sertularida  have  essentially  the  same 
structure  as  in  the  Corynida,  and  each  may  be  compared  to  a 
little  Hydra.  Each,  namely,  consists  of  a  soft,  contractile,  and 
extensile  body,  which  is  furnished  at  its  free  extremity  with 
a  mouth  and  a  circlet  of  prehensile  tentacles,  richly  furnished 
with  thread-cells.  The  mouth  opens  into  a  chamber  which 
occupies  the  whole  length  of  the  polypite,  and  which  is  to  be 
regarded  as  the  combined  body-cavity  and  digestive  sac.  At 
its  lower  end  this  chamber  opens  by  a  constricted  aperture 


DIVISIONS  OF  THE  HYDROZOA. 


67 


into  a  tubular  cavity,  which  is  everywhere  excavated  in  the 
substance  of  the  ccenosarc  (Fig.  17,  b).  The  nutrient  parti- 
cles obtained  by  each  polypite  thus  serve  for  the  support  of 


FIG.  17. — a  Seriularia  (Diphasia)  pinnata,  natural  size ;  a'  Fragment  of  the  same  en- 
larged, carrying  a  male  capsule  (o\  and  showing  the  hydrothecse  (A);  &  Fragment  of 
Campanularia  neglecta  (after  Hincks),  showing  the  polypites  contained  in  their  hy- 
drothecse  (A),  and  also  the  point  at  which  the  ccenosarc  communicates  with  the  stomach 
of  the  polypite  (c). 

the  entire  colony,  and  are  distributed  throughout  the  entire 
organism.  The  nutritive  fluid  prepared  in  the  interior  of  each 
polypite  gains  access  through  the  above-mentioned  aperture 
to  the  cavity  of  the  ccenosarc,  which,  by  the  combined  exer- 
tions of  the  whole  assemblage  of  polypites,  thus  becomes 
filled  with  a  granular  nutritive  liquid.  This  coenosarcal  fluid 
is  in  constant  movement,  circulating  through  all  parts  of  the 
colony,  and  thus  maintaining  its  vitality — the  cause  of  the 
movement  being  probably  due,  in  part,  at  any  rate,  to  the 
existence  of  vibrating  cilia. 

The  process  of  reproduction  varies  somewhat  in  different 
members  of  the  order.  In  all  alike,  however,  the  ordinary 
polypites  are  incapable  of  producing  the  essential  elements 
of  reproduction,  and  for  this  purpose  special  generative  buds 
have  to  be  developed.  In  the  typical  Sertularians  the  re- 
productive buds  are  developed  at  certain  seasons  in  great 
numbers,  and  they  constitute  what  used  to  be  called  the 


68 


INVERTEBRATE  ANIMALS. 


"  ovarian  vesicles  "  or  "  capsules."  These  reproductive  buds 
are  enclosed  in  horny  cups  or  receptacles,  often  of  a  very 
beautiful  shape,  and  much  larger  in  size  than  the  ordinary 
hydrothecae  (Fig.  17,  «,  a'}.  Each  bud  may  be  compared  to  a 
polypite  destitute  of  a  mouth  and  tentacles,  being  composed 
of  a  protuberance  of  the  ectoderm  and  endoderm,  containing 
a  prolongation  from  the  general  cavity  of  the  ccenosarc.  The 
essential  elements  of  reproduction  are  developed  between  the 
ectoderm  and  endoderm  of  the  bud,  and  the  resulting  embryo 
is  finally  liberated  as  a  little  oval  body  covered  with  cilia, 
with  which  it  swims  freely  about,  until  it  meets  with  a  suitable 
locality,  when  it  fixes  itself,  loses  its  cilia,  and  by  budding 
soon  develops  another  colony. 

In  one  division  of  this  group — often  described  as  a  separate 
order,  under  the  name  of  Campanularida — some  points  of 
difference  are  observable.  In  the  typical  Sertularians  the 
little  cups  or  hydro thecas  for  the  polypites  are  placed  on  the 
sides  of  the  branches,  and  they  are  not  stalked  (Fig.  17,  a'), 
while  the  reproductive  elements  are  pro- 
duced in  fixed  buds.  In  the  Campanu- 
larida,  on  the  other  hand  (Fig.  17,  #), 
the  hydrothecae  are  supported  upon 
stalks,  and  are  placed  at  the  ends  of 
the  branches,  while  the  generative  buds 
are  usually  detached  to  lead  an  inde- 
pendent existence.  In  these  forms  the 
reproductive  zooids  or  gonophores  start 
as  simple  buds ;  but  they  become  grad- 
ually developed  into  free  -  swimming 
medusoids,  such  as  have  been  before 
alluded  to.  Each  medusoid  consists  of 
a  little  transparent,  glassy  bell,  from  the 
under  surface  of  which  there  is  sus- 
pended a  modified  polypite,  in  the  form 
of  a  manubrium  (Fig.  18).  The  whole 
organism  swims  gayly  through  the 
water,  propelled  by  the  contractions  of 
the  bell  or  disk ;  and  no  one  would  sus- 
pect now  that  it  was  in  any  way  related 
to  the  fixed,  plant-like  zoophyte  from 

na.  i8.-GonoPhore  of  one  of  which  it  was  originally  budded" off.   The 
the  Campanularida.        central  polypite   is    furnished   with   a 
mouth  at  its  distal  end,  and  the  mouth 
opens  into  a  digestive  sac.    From  the  upper  end  of  this  stomach 


DIVISIONS   OF  THE  HYDROZOA.  69 

proceed  four  radiating  canals  which  extend  to  the  margins  of 
the  bell,  where  they  all  open  into  a  circular  vessel  which  runs 
round  the  mouth  of  the  bell.  From  the  circumference  of  the 
bell  hang  also  a  number  of  delicate  extensile  filaments  or 
tentacles ;  and  the  margin  is  further  adorned  with  a  series  of 
brightly-colored  spots,  which  are  probably  rudimentary  organs 
of  vision  and  hearing.  The  mouth  of  the  bell  is  partially 
closed  by  a  delicate  transparent  membrane  or  shelf,  the  so- 
called  "  veil."  Thus  constituted,  these  beautiful  little  beings 
lead  an  independent  and  locomotive  existence  for  a  longer  or 
shorter  period.  Ultimately  ova  and  sperm-cells  are  produced 
in  special  organs,  which  are  developed  in  the  course  of  the 
radiating  canals  of  the  disk.  The  resulting  embryos  are  minute 
free-swimming  bodies,  covered  with  cilia,  which  finally  fix 
themselves,  and  develop  into  the  plant-like  colonies  from  which 
the  medusoids  were  derived. 


CHAPTER   VL 
SUB-CLASS    SIPHONOPHORA. 

THE  animals  included  under  the  name  of  Siphonophora 
are  often  known  as  the  "  oceanic  Hydrozoa,"  as  they  are  not 
fixed  like  the  Hydroid  zoophytes,  but  are  found  swimming  at 
the  surface  of  the  open  ocean,  far  from  land.  They  are  all 
singularly  delicate  and  beautiful  organisms,  but  they  require 
little  notice  here.  They  are  distinguished  from  the  Hydroid 
zoophytes,  which  we  have  been  just  considering,  by  the  fact 
that  the  hydrosoma  consists  of  numerous  polypites,  united  by 
a  common  trunk  or  ccenosarc,  which  is  very  rarely  branched, 
and  is  never  furnished  with  any  hard  outer  covering  or  poly- 
pary,  so  that  it  remains  permanently  soft  and  flexible  through- 
out life.  As  in  the  Hydroida,  the  reproductive  organs  are  in  the 
form  of  special  buds,  which  have  the  power  of  developing  the 
essential  elements  of  generation,  and  which  are  often  detached 
as  free-swimming  medusoids. 

The  entire  sub-class  is  divided  into  two  great  groups  or 
orders,  and  it  will  be  sufficient  to  consider  shortly  a  typical 
form  of  each.  In  the  first  order — that  of  the  Calycophoridce — 
the  ccenosarc  is  thread-like,  cylindrical,  unbranched,  and  highly 
contractile.  The  cavity  of  the  coenosarc  dilates  at  one  end 
into  a  peculiar  ciliated  chamber,  which  is  the  distinguishing 
character  of  the  order.  The  name  of  Calycophoridce,  (Gr. 
kalux,  a  cup ;  and  phero,  I  bear)  is,  however,  derived  from 
another  circumstance — namely,  that  one  end  of  the  coenosarc 
is  always  furnished  with  a  series  of  bell-shaped  disks,  which 
are  known  as  "swimming-bells"  or  " nectocalyces."  Each 
nectocalyx  consists  of  a  bell-shaped  cup  (Fig.  19,  v,  v'),  at- 
tached by  its  base  to  the  ccenosarc,  and  having  its  cavity 
turned  outward.  In  the  substance  of  the  disk  run  at  least 
four  canals,  which  communicate  with  the  cavity  of  the  coeno- 


SIPHONOPHORA. 


sarc,  and  proceed  to  the  margin  of  the  bell,  where  they  all 
open  into  a  circular  vessel.  The  mouth  of  the  bell  is  also 
furnished  with  a  delicate  ledge,  which  runs  round  its  circum- 
ference, and  is  known  as  the  "  veil."  The  structure,  there- 
fore, of  the  nectocalyces  is  very  similar  to  that  of  an  ordinary 
medusiform  gonophore,  the  chief  difference  being  the  absence 
in  the  former  of  the  central  polypite  or 
manubrium.  The  nectocalyces  are  highly 
muscular,  and  have  the  power  of  alter- 
nately contracting  and  dilating,  thus  driv- 
ing the  whole  organism  through  the  water. 
In  Diphyes  (Fig.  19),  which  may  be  taken 
as  the  type  of  the  group,  there  is  a  long 
thread-like  trunk  or  "  coenosarc  "  (c)  which 
bears  at  intervals  minute  polypites,  each 
of  which  is  protected  by  a  delicate  glassy 
overlapping  plate,  termed  a  "  bract."  At 
one  extremity  of  the  coenosarc  are  two 
large  mitre  -  shaped  swimming  -  bells  or 
nectocalyces  (v,  v'),  by  the  contractions 
of  which  the  entire  organism  is  driven 
through  the  water.  The  ccenosarc  with 
its  polypites  can  be  withdrawn,  when 
necessary,  into  a  kind  of  chamber  be- 
tween the  two  swimming  -  bells ;  but 
when  unretracted  the  organism  often 
attains  a  length  of  several  inches.  Its 
name  is  derived  from  the  fact  that  the 
two  nectocalyces  can  be  separated  from 
the  ccenosarc  by  the  least  touch,  and  it 
was  for  this  reason  originally  supposed 
to  consist  of  two  distinct  animals  loosely 
attached  to  one  another.  The  tentacles 
are  comparatively  speaking  of  great  length, 
and  are  furnished  with  lateral  branches 
containing  numerous  thread-cells.  The 
mouths  of  the  polypites  are  not  pro- 
vided with  a  circlet  of  tentacles,  but  each  has  a  single  long 
tentacle  arising  from  near  its  base.  The  reproductive  organs 
of  the  Catycophoridce  are  in  the  form  of  medusiform  gono- 
phores,  which  are  budded  from  the  stalks  of  the  polypites, 
and  which  are  mostly  detached  to  lead  an  independent  ex- 
istence. 

The  second  order  of  the  oceanic  Hydrozoa  is  that  of  the 


FIG.  \§.—Diphyex  appendi- 
cnlata,  one  of  the  Calyco- 
phoridce  (after  Kolliker). 
•?',  «',  Swimming-bells;  e 
Coenosarc,  carrying  the 
polypites,  each  with  its 
tentacle  and  protected  by 
a  bract. 


72  INVERTEBRATE  ANIMALS. 

PhysophoridcB  (Gr. physa,  a  bladder;  and  phero,  I  carry),  of 
which  the  most  familiar,  though  not  the  most  typical,  example 
is  the  Portuguese  man-of-war,  Physalia  utriculus  (Fig.  20,  a). 
The  Physophoridce  are  distinguished  from  the  organisms 
which  we  have  been  just  considering  by  the  fact  that  one 
extremity  of  the  ccenosarc  is  developed  into  a  structure  which 
is  known  as  the  "  float "  or  "  pneumatophore  "  (Gr.  pneuma, 
air;  and  phero,  I  carry).  The  float  contains  a  larger  or 
smaller  sac,  composed  of  some  elastic,  horny  substance,  proba- 
bly chitine,  often  communicating  with  the  exterior  by  one  or 
more  apertures,  and  always  more  or  less  completely  filled  with 
air.  This  sac  is  enclosed  in  a  reflection  of  the  ectoderm  and 
endoderm,  so  that  it  is  really  outside  the  cavity  of  the  cceno- 
sarc. The  function  of  the  float  is  no  doubt  that  of  enabling 
the  organism  to  maintain  its  position  at  the  surface  of  the 
sea.  As  in  the  Calycophoridce,  the  ccenosarc  is  always  per- 
fectly flexible,  contractile,  and  soft,  and  is  never  furnished 
with  any  chitinous  covering  or  poly  pa  ry.  There  may  or  may 
not  be  swimming-bells,  and  the  tentacles  are  very  complicated 
in  structure,  and  often  attain  a  length  of  many  inches.  The 
polypites  present  no  special  points  of  interest,  but  are  often 
furnished  with  the  protective  plates,  which  have  been  already 
spoken  of  as  "  bracts." 

As  a  good  example  of  the  Physophoridce,  the  Portuguese 
man-of-war  may  be  taken  (Fig.  20,  a).  It  is  composed  of  a 
large,  spindle-shaped  float,  often  of  several  inches  in  length, 
upon  the  under  surface  of  which  are  arranged  a  number  of 
polypites,  together  with  highly-contractile  tentacles  of  great 
length,  and  reproductive  organs.  The  tentacles  are  richly 
furnished  with  thread-cells  ;  and  it  has  the  power  of  stinging 
very  severely.  Physalia  is  commonly  found  floating  at  the 
surface  of  tropical  and  sub-tropical  seas,  and  fleets  of  it  are 
occasionally  driven  upon  temperate  shores. 

Another  very  beautiful  member  of  the  Physophoridce  is 
the  Velella  vulgaris,  which  occurs  abundantly  in  many  seas. 
It  is  about  two  inches  in  length  by  one  and  a  half  in  height. 
One  end  of  the  ccenosarc  is  greatly  expanded  and  flattened  out 
into  an  oval  disk,  which  carries  a  vertical  triangular  crest, 
running  obliquely  across  its  upper  surface  (Fig.  20,  b).  The 
whole  organism  is  semi-transparent  and  of  a  beautiful  bluish 
color,  and  it  floats  at  the  surface  of  the  sea  with  the  vertical 
crest  exposed  to  the  influence  of  the  wind,  and  thus  officiating 
as  a  sail.  From  the  under  surface  of  the  disk  are  suspended 
the  various  appendages  of  the  organism,  consisting  of  a  single 


SIPHONOPHORA. 


large  central  polypite,  a  number  of  processes,  like  polypites 
in  shape,  and  carrying  medusiform  gonophores ;  and  lastly,  a 
single  series  of  tentacles  which  arise  from  the  ccenosarc  quite 
independently  of  the  polypites. 


FIG.  20.— a  Portuguese  man-of-war  (after  Huxley);  6  Vetella  vulgaris  (after  Gospe). 


CHAPTER   VII. 
SUB-CLASS  DISCOPHORA. 

THE  group  of  Hydrozoa  here  spoken  of  as  Discophora  or 
Medusidae  comprises  most  of  the  familiar  organisms  known  to 
visitors  at  the  sea-side  as  sea-jellies,  jelly-fishes,  or  sea-nettles ; 
this  last  name  being  derived  from  the  power  possessed  by 
some  of  them  of  stinging  pretty  severely  in  virtue  of  the  pos- 
session of  numerous  thread-cells.  Under  the  name,  however, 
of  sea-jellies  are  included  a  number  of  large  organisms,  ex- 
tremely common  at  certain  seasons  in  our  seas,  but  now 
known  to  be  properly  referable  to  another  group  of  the  Hy- 
drozoa (viz.,  Lucernarida).  It  is  these  large  forms  which 
alone  possess  any  power  of  stinging  man,  and  to  these  the 
term  of  "  sea-nettles  "  ought  properly  to  be  restricted.  They 
are  better  known  under  the  name  of  "  hidden-eyed  "  Medusae, 
applied  to  them  by  the  late  Edward  Forbes.  Under  the 
present  group  of  the  Discophora  are  included  only  a  number 
of  small  jelly-fishes,  found  in  great  abundance  at  certain 
times,  floating  in  the  open  sea,  but  nevertheless  very  little 
known  to  the  general  public  in  consequence  of  their  very 
minute  size.  These  delicate  and  diminutive  organisms  were 
originally  described  by  Edward  Forbes,  for  reasons  to  be 
immediately  stated,  as  the  "  naked-eyed  "  Medusae.  It  is  now 
known,  however,  that  most  of  these  naked-eyed  Medusce  are 
in  reality  nothing  more  than  the  free-swimming  generative 
buds,  or  medusiform  gonophores,  produced  by  budding  from 
so  many  of  the  other  Hydrozoa,  and  then  detached,  as  we 
have  formerly  seen,  to  lead  an  independent  existence.  That 
this  is  their  true  nature,  is  shown  by  the  fact  that  the  eggs 
which  they  produce  develop  themselves,  not  into  fresh  Me- 
dusce, but  into  various  other  forms  of  Hydrozoa,  which  are 
fixed  or  oceanic.  Under  these  circumstances,  therefore,  the 


DISCOPHORA.  75 

naked-eyed  Medusae,  which  can  be  shown  to  be  of  this  nature, 
cannot,  of  course,  be  regarded  as  distinct  animals  at  all.  Still, 
there  remains  a  considerable  group  of  naked-eyed  Medusce  to 
which  this  explanation  has  not  hitherto  been  shown  to  apply. 
In  most  of  the  members  of  this  group  the  course  of  develop- 
ment is  quite  unknown,  and  therefore  their  true  nature  is  a 
matter  of  doubt.  Two  families,  however,  of  this  group  are 
stated  to  produce  eggs  which  develop  directly  into  Medusce, 
such  as  those  which  gave  origin  to  the  eggs ;  and,  if  this  ob- 
servation is  confirmed,  these,  at  any  rate,  must  be  regarded 
as  true  Discophora.  In  the  mean  while,  therefore,  it  is  best 
to  regard  the  group  of  the  Discophora  or  Medusidce  as  of  a 
questionable  nature,  and  as  including  forms  which  may  ulti- 
mately be  shown  to  be  nothing  more  than  the  detached  zo5ids 
of  other  Hydrozoa.  Under  these  circumstances  it  will  not  be 
requisite  to  do  more  than  very  briefly  to  describe  the  anatomical 
structure  of  a  typical  Medusid  /  and  this  is  the  less  necessary, 
since  it  will  be  seen  at  once  that  the  structure  is  in  all  essential 
respects  identical  with  what  has  been  already  described  in 
speaking  of  the  free  medusiform  gonophores  of  the  Hydroid 
zoophytes. 

In  all  the  naked-eyed  Medusce,  of  which  Modeeria  (Fig.  21) 


FIG.  21. — Naked-eyed  Medusae,  a  Sarsia  gemmifera;   T>  Modeeria  fomnosa ;  c  Polyxe- 
nia  Alderi  (after  Gosse). 


76  INVERTEBRATE  ANIMALS. 

may  be  taken  as  a  good  example,  the  general  structure  is  briefly 
as  follows :  The  hydrosoma  is  perfectly  free  and  is  oceanic, 
being  found  swimming  near  the  surface  in  the  open  ocean. 
The  body  is  composed  of  a  thick,  transparent,  gelatinous  disk 
or  swimming-bell  (the  nectocalyx),  by  the  pulsations  of  which 
the  animal  is  driven  through  the  water.  From  the  under 
surface  or  roof  of  this  bell-shaped  disk  is  suspended  a  single 
polypi te  (the  manubrium),  which  bears  to  the  disk  the  same 
relative  position  as  the  clapper  does  to  an  ordinary  hand- 
bell. The  distal  end  of  the  central  polypite  is  furnished  with 
a  mouth,  the  lips  of  which  are  often  prolonged  into  four 
longer  or  shorter  lobes  or  processes.  The  mouth  opens  into  a 
digestive  sac,  occupying  the  axis  of  the  polypite ;  and  from 
the  upper  end  of  this  proceed  four  radiating  canals,  which 
run  in  the  substance  of  the  disk  to  its  margin,  where  they  are 
united  by  a  single  circular  vessel,  the  whole  system  con- 
stituting the  so-called  "  gastro-vascular  "  canals.  The  margin 
of  the  bell  is  narrowed  by  a  kind  of  shelf,  which  runs  round 
the  whole  circumference,  leaving  a  central  aperture,  and  which 
is  known  as  the  "  veil."  From  the  margin  of  the  disk  hang 
more  or  less  numerous  tentacles,  which  are  hollow  processes 
of  the  ectoderm  and  endoderm,  and  which  communicate  with 
the  circular  vessel  of  the  canal-system.  Also  round  the  cir- 
cumference of  the  swimming-bell  are  disposed  certain  "  margi- 
nal bodies,"  which  are  doubtless  organs  of  sense.  Some  of 
these  marginal  bodies  consist  of  little  rounded  sacs  or  "  vesi- 
cles," filled  with  a  transparent  fluid,  and  containing  mineral 
particles,  apparently  of  carbonate  of  lime.  These  are  probably 
rudimentary  organs  of  hearing.  Others  of  the  marginal  bodies 
are  in  the  form  of  little  masses  of  coloring-matter  or  pigment, 
often  of  a  strikingly  bright  color,  enclosed  in  distinct  cavities. 
These  are  known  as  the  "  pigment-spots "  or  "  eye-specks," 
and  they  are  believed  to  be  rudimentary  organs  of  vision. 
They  are  placed  in  a  conspicuous  and  unprotected  position  on 
the  margin  of  the  disk,  and  hence  these  organisms  were  termed 
"  naked-eyed  "  Medusae,  by  Edward  Forbes.  The  reproductive 
organs  are  mostly  developed  in  the  course  of  the  radiating 
gastro-vascular  canals,  but  are  sometimes  situated  in  the  walls 
of  the  central  polypite.  The  above  is  the  essential  structure 
of  any  of  the  ordinary  naked-eyed  Medusm  ;  and  it  is  hardly 
necessary  to  remark  that  it  is  exactly  similar  to  what  has 
been  formerly  described  as  distinguishing  the  undoubted  free- 
swimming  reproductive  buds  of  the  fixed  Hydrozoa.  The 
probabilities,  therefore,  as  before  said,  are  in  favor  of  the  belief 


DISCOPHORA.  77 

that  the  entire  group  of  the  Discophora  will  have  to  be  ulti- 
mately done  away  with. 

The  naked-eyed  Medusce  are  all  exceedingly  elegant  and 
attractive,  when  examined  in  a  living  condition,  resembling 
little  bells  of  the  most  transparent  glass,  adorned  here  and 
there  with  the  most  brilliant  colors.  They  occur,  in  their 
proper  localities  and  at  proper  seasons,  in  enormous  numbers, 
and  they  constitute  one  of  the  staple  articles  of  diet  to  the 
Greenland  whale.  They  are  mostly  phosphorescent,  or  capa- 
ble of  giving  out  light  at  night,  and  they  appear  to  be  one  of 
the  principal  sources  of  the  luminosity  of  the  sea.  It  does  not 
seem,  however,  that  they  phosphoresce  unless  disturbed  or 
irritated  in  some  way. 


CHAPTER  VIII. 

SUB-CLASSES  LUCERNARIDA  AND  GRAPTOLITID^E. 

THE  last  remaining  group  of  the  living  Hydrozoa  is  that 
of  the  I/ucernarida  (Lat.  lucerna,  a  lamp),  under  which  name 
are  included  a  considerable  number  of  forms,  differing  from 
one  another  to  a  great  extent  in  exter- 
nal appearance.  It  will  be  sufficient 
here  to  describe  one  or  two  typical 
forms. 

One  group  of  the  Lucernarida  is 
represented  by  Lucernaria  itself  (Fig. 
22),  which  occurs  not  uncommonly  in 
temperate  seas.  In  Lucernaria  we  have 
a  cup-shaped  body,  of  a  more  or  less 
gelatinous  consistence,  usually  found 
attached  by  its  smaller  extremity  to 
sea-weeds,  this  end  of  the  body  being 
developed  into  a  small  sucker.  Like 
the  Hydra,  however,  Lucernaria  is  not 
fixed,  but  can  detach  itself  at  will,  and 
can  even  swim  freely  by  means  of  the 
alternate  contraction  and  expansion  of 
the  cup-shaped  body  (or  "  umbrella," 
as  it  is  termed).  Round  the  margin  of 
the  cup  are  tufts  of  short  tentacular 
processes,  and  in  its  centre  is  fixed  a 
single  polypite,  furnished  with  a  four- 

FiG.22.-Two  specimens  of  LU-  lobed  mouth.     The  essential  elements 
cemaria  auricula  attached  of  reproduction  are  developed  within 
?ohnPSton).°fSea"Weed(after  the  body  of  Lucernaria  itself,  and  it 
does  not  give  off  any  generative  buds, 
as  so  commonly  occurs  in  other  forms. 


LUCERNARIDA  AND  GRAPTOLITIDJ3.  79 

Another  type  of  the  Lucernarida  is  represented  by  the 
organisms  formerly  termed  "  hidden  -  eyed  "  Medusas^  and 
familiarly  known  as  sea-nettles  or  sea-blubbers.  Every  sea- 
side visitor  is  familiar  with  the  great  circular  disks  of  jelly 
which  are  left  upon  the  sands  by  the  retreating  tide  during 
the  summer  months ;  and  many  must  have  noticed  on  a  calm 
day  the  large,  transparent  disks  of  these  same  creatures  slowly 
flapping  their  way  through  the  water.  Not  a  few,  too,  must 
have  learned  by  painful  experience  that  some  of  these  singular 
organisms  have  the  power  of  stinging  most  severely,  if  in- 
cautiously handled.  The  forms  included  under  the  old  name 
of  "  covered-eyed  "  Medusw  differ  considerably  from  one  an- 
other in  their  nature,  and  even  in  their  structure,  though  they 
all  present,  in  spite  of  their  much  greater  size,  a  decided  re- 
semblance to  the  naked-eyed  Medusm  already  described.  Some 
of  the  covered-eyed  Medusae  produce  eggs  which  are  developed 
into  organisms  resembling  themselves ;  but  most  of  them  are 
now  known  to  be  nothing  more  than  the  free-swimming  re- 
productive buds  of  minute  rooted  Hydrozoa.  It  will  be  suf- 
ficient here  to  describe  shortly  the  life-history  of  one  of  the 
more  remarkable  forms  of  this  section. 

If  we  commence  with  the  young  form  of  one  of  these  sin- 


FIG.  23.— Development  of  Lucernarida  (Chrysaora).  a  Ciliated  embryo;  b  Hydra-tuba; 
c  Hydra-tuba  beginning  to  divide  by  transverse  cleavage ;  d  The  cleavage  still  further 
advanced ;  e  A  form  in  which  the  cleavage  has  proceeded  still  further,  and  a  fresh  circle 
of  tentacles  has  been  produced  near  the  base ;  /  Free-swimming,  generative  zooid,  pro- 
duced by  fission  from  the  Hydra-tuba. 

gular  animals,  we  find  that  the  egg  gives  origin  to  a  little 
microscopic  ciliated  body,  which  swims  about  freely  by  means 
of  the  cilia  with  which  its  surface  is  covered  (Fig.  23,  a). 


80  INVERTEBRATE  ANIMALS. 

This  little  body,  on  finding  a  suitable  locality,  fixes  itself  by 
one  end,  and  develops  a  mouth  and  tentacles  at  the  other, 
when  it  is  known  as  a  "Hydra-tuba"  (Fig.  23,  #),  from  its 
resemblance  in  shape  to  the  fresh-water  polype  or  Hydra. 
The  Hydra-tuba  is  only  about  half  an  inch  in  height,  and  it 
possesses  the  power  of  forming  large  colonies  by  gemmation, 
while  it  is  incapable  of  developing  the  essential  elements  of 
reproduction.  Under  certain  circumstances,  however,  repro- 
ductive zoftids  are  produced  by  the  following  singular  process : 
The  Hydra-tuba  becomes  elongated,  and  exhibits  a  number 
of  transverse  grooves  (Fig.  23,  c).  These  grooves  go  on  get- 
ting deeper  and  deeper,  and  become  lobed  at  their  margins, 
till  the  whole  organism  assumes  the  aspect  of  a  pile  of  saucers 
placed  one  above  the  other  (Fig.  23,  d).  The  tentacles  now 
disappear,  and  a  fresh  circle  is  formed  close  to  the  base  of  the 
Hydra-tuba  (Fig.  23,  e).  Finally,  all  the  saucer-like  segments 
above  the  new  circle  of  tentacles  drop  off  one  by  one,  and  pre- 
sent themselves  in  the  form  of  independent,  free-swimming 
Medusae,  (Fig.  23,/).  These  reproductive  zooids  or  Medusae 
eat  voraciously,  and  increase  rapidly  in  size,  becoming  not 
only  comparatively,  but  often  actually,  gigantic.  Thus,  in 
one  case  the  reproductive  zoo'id  has  been  known  to  attain  a 
size  of  seven  feet  across,  with  tentacles  fifty  feet  in  length, 
though  the  fixed  organism  from  which  it  was  produced,  wras 
no  more  than  half  an  inch  in  height.  These  gigantic  repro- 
ductive bodies  live  an  independent  life  until  they  are  able  to 
produce  ova  and  sperm-cells,  when  they  die.  The  fertilized 
egg,  however,  develops  itself,  not  into  the  monstrous  organism 
by  which  it  was  produced,  but  into  the  little  fixed  sexless 
Hydra-tuba,  from  which  the  generative  bud  was  detached.  We 
have,  then,  here  another  instance  of  the  so-called  "  alterna- 
tion of  generations." 

It  is  now  known,  then,  that  most  of  the  great  sea-blubbers 
which  abound  around  our  coasts  in  summer  are  really  the 
detached  reproductive  buds  of  minute  fixed  Hydrozoa  ;  and  it 
may  be  as  well  to  mention  the  leading  features  in  their  struct- 
ure, and  the  points  by  which  they  may  be  distinguished  from 
the  smaller  or  naked-eyed  Medusae,  to  which  they  have  a  de- 
cided superficial  likeness.  In  the  commonest  forms  of  these 
zooids  (such  as  the  familiar  sea-blubbers,  Aurelia  and  Cyaned)^ 
the  body  consists  of  a  great  bell-shaped  gelatinous  disk  or 
"  umbrella,"  from  the  roof  of  which  is  suspended  a  single 
polypite,  the  lips  of  which  are  extended  into  lobed  processes, 
often  extending  far  below  the  margin  of  the  disk  (Fig.  24). 


LUCERNARIDA  AND   GRAPTOLITDLE.  81 

The  digestive  cavity  of  the  polypite  gives  out  from  its  upper 
extremity  a  series  of  radiating  gas tro- vascular  canals,  which 
proceed  toward  the  margin  of  the  umbrella.  These  radiating 
canals  are  never  less  than  eight  in  number,  and  on  their  way 
to  the  margin  of  the  disk  they  break  up  into  a  great  number 
of  smaller  vessels,  which  unite  with  one  another  to  form  a 
complicated  net-work.  At  the  margin  of  the  bell  they  all 


FIG.  24.— Generative  zooid  of  one  of  the  Lucernarida  (Clirysaora  hysoscclla).    (After 

Gosse.) 

open  into  a  circular  vessel,  which  in  turn  sends  processes  into 
a  series  of  marginal  tentacles,  which  are  often  of  extraordinary 
length.  Besides  the  tentacles,  the  margin  of  the  umbrella  is 
provided  with  a  number  of  marginal  bodies,  each  of  which 
consists  of  a  little  collection  of  pigment  or  "  eye-speck,"  and  a 
little  sac  filled  with  fluid  and  containing  mineral  particles. 
Each  of  these  marginal  bodies  is  covered  and  concealed  from 
view  by  a  kind  of  hood  derived  from  the  ectoderm.  Hence 
the  name  of  "hidden-eyed"  Medusae  applied  to  these  forms, 
in  contradistinction  to  the  "  naked-eyed  "  Medusas,  in  which 
the  eye-specks  are  exposed  to  view.  The  reproductive  organs 
are  usually  of  some  bright  color,  and  "  form  a  conspicuous 
cross  shining  through  the  thickness  of  the  disk." 


82  INVERTEBRATE  ANIMALS. 

From  the  above  description  it  will  be  evident  that  there  is 
considerable  resemblance  between  the  so-called  "  hidden-eyed" 
Medusae,  or  the  reproductive  zoOids  of  many  of  i\^Q  Lucernarida, 
and  the  medusiform  gonophores  of  so  many  of  the  Hydrozoa, 
as  well  as  the  true  Discophora  or  naked-eyed  Medusae.  The 
differences, however,  between  them  are  these:  The  swimming- 
disk  of  the  naked-eyed  Medusae  and  of  any  medusiform  gono- 
phore  is  furnished  at  its  mouth  with  an  internal  shelf  or  veil ; 
the  radiating  gastro-vascular  canals  are  very  rarely  more 
than  four  in  number,  and,  should  they  subdivide  (as  in  rare 
cases  they  do),  they  do  not  form  an  intricate  net-work;  lastly, 
the  marginal  bodies  are  simply  placed  in  an  uncovered 
situation  on  the  margin  of  the  disk.  In  the  reproductive 
zooids  of  the  Lucernarida  or  hidden-eyed  Medusae,  on  the 
other  hand,  the  swimming-disk  or  umbrella  is  destitute  of 
any  marginal  shelf  or  veil ;  the  radiating  gastro-vascular 
canals  are  never  less  than  eight  in  number,  and  they  split  up 
into  numerous  branches,  which  unite  to  form  an  intricate  net- 
work ;  lastly,  the  marginal  bodies  are  concealed  from  view  by 
a  kind  of  hood. 

There  still  remains  another  family  of  the  Lucernarida  (viz., 
Rhizostomidoe)  in  which  the  reproductive  process  is  carried  on 
in  the  same  way  as  in  the  forms  we  have  just  described,  but 
the  structure  of  the  reproductive  zooids  is  somewhat  different. 
In  these,  as  in  Rhizostoma,  the  generative  zob'id  is  much 
like  those  just  mentioned  ;  but  the  umbrella  is  destitute  of 
marginal  tentacles ;  and,  in  place  of  a  single  central  polypite, 
there  hangs  from  the  under  surface  of  the  umbrella  a  com- 
plex tree-like  mass,  the  branches  of  which  end  in,  and  are 
covered  by,  small  polypites  and  club-shaped  tentacles.  The 
umbrella  itself  does  not  exhibit  any  difference  as  compared 
with  those  already  described,  but  the  ova  are  produced  in 
a  genital  cavity  which  is  placed  on  the  under  surface  of  the 
umbrella. 

SUB-CLASS  GRAPTOLITID.E. — Before  leaving  the  Hydrozoa,  it  will  be  as  well 
to  notice  very  briefly  a  group  of  extinct  organisms  which  certainly  belong  to 
this  class,  and  which  probably  find  their  nearest  allies  in  the  Sertularians. 
The  Graptolitidce  are  without  a  single  living  representative,  and  their  anti- 
quity is,  indeed,  very  high,  since  it  is  doubtful  if  they  ever  pass  above  the 
group  of  rocks  known  to  geologists  as  the  Silurian  formation.  The  most 
typical  forms  of  the  group  agree  with  the  living  Sertularians  in  having  a 
horny  polypary,  and  in  having  the  polypites  protected  by  little  horny  cups 
or  hydrothecae,  all  springing  from  a  common  flesh  or  cocnosarc.  The  typical 
Graptolites,  however,  differ  from  all  known  Sertularians  in  the  fact  that  the 
hydrosoma  was  not  fixed  to  any  solid  object,  but  was  permanently  free. 


LUCERNARIDA  AND  GRAPTOLITID.E.  83 

Most  of  them,  also,  exhibit  a  very  anomalous  and  remarkable  structure, 
termed  the  "  solid  axis."  This  is  a  peculiar  fibrous  rod,  which  no  doubt 
served  to  strengthen  the  polypary,  and  which  is  often  prolonged  beyond  one 
or  both  ends  of  the  polypary  in  a  naked  state.  There  is  also  good  evidence 
that  the  reproductive  process  in  the  Graptolites  was  carried  on  in  a  manner 
somewhat  similar  to  what  is  seen  in  the  living  Sertularians — namely,  by 
means  of  reproductive  buds  enclosed  in  horny  capsules.  Graptolites  most 
usually  present  themselves  as  beautiful  silvery  impressions,  covering  the  sur- 
face of  the  black  shales  of  various  parts  of  the  Silurian  system. 


CHAPTER   IX. 

ACTINOZOA. 

THE  second  great  class  of  the  Coelenterata  is  that  of  the 
Actinozoa,  comprising  the  sea-anemones  and  their  allies,  the 
corals,  the  sea-pens,  the  sea-shrubs,  and  various  other  organ- 
isms. They  are  all  defined  as  Ccelenterate  animals  in  which 
there  is  a  distinct  digestive  sac  which  opens  below  into  the 
general  cavity  of  the  body,  but  is  nevertheless  separated  from 
the  body-walls  by  an  intervening  space,  which  is  divided  into 
a  number  of  vertical  compartments  by  a  series  of  partitions 
or  "  mesenteries"  to  the  faces  of  which  the  reproductive  organs 
are  attached.  The  Actinozoa  (Fig.  12),  therefore,  differ  fun- 
damentally from  the  Hydrozoa  in  this,  that  whereas  in  the 
latter  the  digestive  cavity  is  identical  with  the  body-cavity, 
in  the  former  there  is  a  distinct  digestive  sac,  which  opens 
truly  into  the  body-cavity,  but  is  nevertheless  separated  from 
it  by  an  intervening  space.  The  result  of  this  is,  that  while 
the  body  of  a  Hydrozodn  exhibits  on  transverse  section  a 
single  tube  only,  formed  by  the  walls  of  the  combined  diges- 
tive and  somatic  cavity,  the  body  of  an  Actinozodn  exhibits 
two  concentric  tubes,  one  formed  by  the  digestive  sac  and  the 
other  by  the  general  walls  of  the  body  (Fig.  25,  A).  Further, 
in  the  Actinozoa  the  reproductive  organs  are  always  internal, 
and  are  never  in  the  form  of  external  processes  of  the  body- 
wall  as  in  the  Hydrozoa. 

In  their  minute  structure  the  tissues  in  the  Actinozoa  dif- 
fer little  from  those  of  the  Hydrozoa.  The  body  is  essen- 
tially composed  of  two  fundamental  layers — an  ectoderm  and 
endoderm ;  but  there  are  often  well-developed  layers  of  mus- 
cular fibres,  somewhat  obscuring  this  simplicity  of  structure. 
Thread-cells  are  most  commonly  present  in  abundance.  Cilia 
are  very  generally  developed,  especially  in  the  endoderm  lining 


ACTINOZOA. 


85 


the  body-cavity,  where  they  serve  to  maintain  a  circulation  of 
the  contained  fluids.  The  only  digestive  apparatus  consists 
of  a  tubular  or  sac-like  stomach,  which  opens  inferiorly 
directly  into  the  body-cavity  (Fig.  12,  a),  and  communicates 


FIG.  25.— A.  Transverse  section  of  an  Actinosoon.  a  Digestive  sac;  b  Outer- wall  of  the 
body  or  ectoderm ;  6'  Endoderm ;  m  Mesenteries,  connecting  the  stomach  with  the 
body- walls,  and  dividing  the  space  between  the  two  into  a  number  of  vertical  chambers. 
B.  Transverse  section  of  the  body  of  a  Hydrozoon,  showing  the  single  tube  formed  by 
the  walls  of  the  body. 

with  the  outer  world  through  the  mouth.  A  nervous  system 
has  not  been  shown  to  exist  in  any  of  the  Actinozoa  except 
the  Ctenophora,  and  in  none  are  there  any  traces  of  a  circula- 
tory system.  Distinct  reproductive  organs  are  always  present, 
and  true  sexual  reproduction  occurs  in  all  the  members  of  the 
class.  In  a  great  many  forms,  however,  of  the  Actinozoa  we 
have  composite  organisms  or  colonies,  produced  by  a  process 
of  "  continuous  "  gemmation  or  fission,  the  zoOids  thus  origi- 
nated remaining  attached  to  one  another.  In  these  cases — 
as  in  most  of  the  corals — the  separate  beings  or  zo5ids  thus 
produced  are  termed  "  polypes,"  the  term  "  polypite  "  being 
restricted  to  the  Hydrozoa.  In  the  simple  Actinozoa,  how- 
ever, such  as  the  sea-anemones,  the  term  "  polype  "  is  applied 
to  the  entire  organism,  as  consisting  of  no  more  than  a  single 
alimentary  region.  It  follows  from  this,  that  the  entire  body 
of  any  Actinozoon  may  be  composed  of  a  single  polype,  or 
of  several  such  produced  by  budding  or  cleavage,  and  united 
to  one  another  by  a  common  connecting  structure  or  ccenosarc. 
Most  of  the  Actinozoa  are  permanently  fixed,  like  the  corals ; 
some,  like  the  sea-anemones,  possess  a  limited  amount  of 
locomotive  power ;  and  one  order,  the  Ctenophora,  is  com- 
posed of  highly-active  free-swimming  organisms.  Some  of 
them  are  unprovided  with  hard  structures  or  supports  of  any 
kind,  as  the  sea-anemones  and  Ctenophora  ;  but  a  great  many 
5 


86 


INVERTEBRATE  ANIMALS. 


secrete  a  calcareous  or  horny  skeleton  or  framework  which  is 
known  as  the  "  coral  "  or  "  corallum." 

The  Actinozoa  are  divided  into  four  orders^-viz.,  the  Zoan- 
tharia, the  Alcyonaria,  the  Hugosa,  and  the  Ctenophora. 


OEDER  I.  ZOANTHAEIA  (Gr.  zoon,  animal 


anthos,  flower). 

—  The  Zoantharia  comprise  those  Actinozoa  in  which  the 
polypes  are  furnished  with  smooth,  simple,  usually  numerous 
tentacles,  which,  like  the  mesenteries,  are  in  multiples  of  five 
or  six.  The  Zoantharia  are  divided  into  three  groups,  dis- 
tinguished from  one  another  by  the  presence  or  absence  of  a 
coral,  and  by  its  structure  when  present. 

The  first  of  these  groups  is  termed  Zoantharia  malacoder- 
mata,  or  "  soft-skinned  "  Zoantharia,  because  the  polypes  are 
either  wholly  destitute  of  a  coral,  or,  if  there  is  one,  it  consists 
merely  of  little  scattered  needles  or  spicules  of  carbonate  of 
lime.  Generally,  too,  the  organism  is  simple,  and  consists  of 


FIG.  26.— Morphology  ofActinidce.   a  Actinia  rosea  ;  &  Arachnactis  albida  (after  Gosse).. 

no  more  than  a  single  polype.  The  best  known  of  the  mem- 
bers of  this  group  are  the  beautiful  sea-anemones  or  animal- 
flowers  (Actinidce),  which  occur  so  plentifully  on  every  coast 
(Fig.  26,  a).  It  will  be  as  well  to  describe  the  structure  of  a 
sea-anemone  somewhat  in  detail,  as  in  this  way  a  clear  notion 
may  be  obtained  of  the  general  anatomy  of  the  Actinozoa. 
The  body  of  an  ordinary  sea-anemone  (Fig.  26,  a)  is  a  truncated 
cone  or  short  cylinder,  termed  the  "  column,"  and  is  of  a  soft, 
leathery  consistence.  The  two  ends  of  the  column  are  termed 


ACTINOZOA.  87 

respectively  the  "  base  "  and  the  "  disk,"  the  former  constitut- 
ing a  kind  of  sucker,  by  means  of  which  the  animal  can  attach 
itself  at  will,  while  the  mouth  is  placed  in  the  centre  of  the 
latter.  The  mouth  is  surrounded  by  a  flat  space,  destitute  of 
appendages,  and  the  circumference  of  the  disk  is  in  turn  sur- 
rounded by  numerous  simple  tubular  tentacles,  arranged  in 
alternating  rows.  The  tentacles  consist  of  both  ectoderm  and 
endoderm,  enclosing  a  tube  which  communicates  with  the 
body-cavity.  By  the  muscular  contraction  of  the  walls  of  the 
column,  the  fluid  contained  in  the  body-chambers  can  be  forced 
into  the  tentacles,  which  can  be  thus  protruded  a  great  length, 
while  they  can  also  be  usually  retracted.  In  some  cases  the 
tentacles  are  furnished  with  perforations  at  their  extremities. 
The  mouth  (see  Fig.  12,  a)  leads  directly  into  the  stomach, 
which  is  a  wide,  membranous  tube,  opening  by  a  wide  aperture 
into  the  body-cavity  below,  and  extending  about  half-way  be- 
tween the  mouth  and  the  base.  The  wide  space  between  the 
stomach  and  body-walls  is  subdivided  into  a  number  of  sepa- 
rate compartments  by  radiating  vertical  plates,  which  are 
called  the  "  mesenteries,"  and  to  the  faces  of  which  the  re- 
productive organs  are  attached,  in  the  form  of  reddish  bands, 
containing  either  ova  or  sperm- cells.  Below  the  stomach, 
attached  to  the  free  edges  of  the  mesenteries,  are  a  series  of 
singularly  twisted  threads  or  cords  (Fig.  12,  c),  which  are 
filled  with  thread-cells,  and  are  termed  "craspeda."  The 
function  of  these  is  not  well  understood ;  but  it  is  believed 
that  in  some  cases  they  can  be  emitted  through  apertures, 
which  are  occasionally  found  in  the  walls  of  the  column.  The 
sea-anemones  are  mostly  to  be  found  between  tide-marks,  in 
rock-pools,  or  on  ledges  of  stone,  adhering  by  means  of  the 
expanded  base.  They  are  not,  however,  permanently  fixed, 
but  can  change  their  place  at  will.  In  the  nearly  allied 
llyanthus  and  Arachnactis  (Fig.  26,  I)  the  base  is  tapering, 
and  it  appears  that  the  animal  spends  the  greater  part  of  its 
existence  in  an  unattached,  free  condition.  The  true  sea- 
anemones,  as  already  said,  are  all  simple,  each  consisting  of 
a  single  polype ;  but  there  are  closely-related  forms  (such  as 
Zoanthus)  in  which  the  organism  is  compound,  consisting  of 
numerous  polypes  united  by  a  creeping,  fleshy  trunk  or  cceno- 
sarc. 

The  second  group  of  the  Zoantharia  is  termed  that  of  the 
Zoantharia  sclerodermata,  from  the  nature  of  the  skeleton  or 
coral.  In  this  group  are  all  the  so-called  "reef-building" 
corals,  which  are  the  makers  of  the  well-known  "  coral-reefs." 


88  INVERTEBRATE  ANIMALS. 

The  members  of  this  group  all  possess  the  power  of  secreting 
carbonate  of  lime  within  their  tissues,  so  as  to  form  a  more 
or  less  continuous  skeleton  or  corallum.  Froni  the  fact  that 
this  corallum  is  secreted  by  the  inner  layer  of  the  polypes, 
and  is  therefore  truly  within  the  body,  it  is  said  to  be  "  sclero- 
dermic,"  in  opposition  to  the  kind  of  coral  produced  by  other 
forms  (such  as  the  red  coral),  where  the  skeleton  is  secreted 
by  the  outer  layer  of  the  polypes,  and  is  therefore  outside 
them.  In  this  latter  case  the  coral  is  said  to  be  "  sclerobasic." 
(For  illustrations  of  these  different  kinds  of  corals,  see  Fig. 
29.)  In  the  typical  form  of  sclerodermic  coral,  the  skeleton  is 
in  the  form  of  a  conical  cup,  the  upper  part  of  which  is  hol- 
low. The  lower  part  is  divided  into  a  series  of  compartments 
by  vertical  plates,  which  are  called  the  "  septa,"  and  which 
correspond  to  the  mesenteries  of  the  living  animal.  Some- 
times the  space  contained  within  the  walls  of  the  cup  cr 
"  corallite"  is  broken  up  by  horizontal  plates  called  "tabulas;" 
but,  when  these  are  present,  there  are  generally  no  septa.  In 
the  form  of  coral  just  described  we  have  a  single  corallite, 
produced  by  one  polype,  and  this  simple  condition  may 
be  maintained  throughout  life.  In  the  great  majority  of 
cases,  however,  the  polypes  bud,  so  as  to  form  a  colony,  all 
bound  together  by  a  common  flesh  or  ccenosarc.  When  such 
a  colony,  therefore,  produces  a  sclerodermic  coral,  in  place 
of  a  single  corallite,  we  have  a  composite  skeleton  composed 
of  a  number  of  little  cups  or  corallites,  each  of  which  was 
produced  by  one  polype,  and  all  of  which  are  united  by  means 
of  a  common  calcareous  basis  secreted  by  the  ccenosarc  (Fig. 
29,  a). 

In  accordance  with  their  mode  of  formation,  an  ordinary 
compound  sclerodermic  coral  may  be  distinguished  from  a 
sclerobasic  coral  by  the  fact  that  it  would  show  a  number  of 
little  cups  in  which  the  polypes  were  contained,  whereas  these 
cups  would  be  absent  in  the  latter.  In  accordance,  also,  with 
the  fundamental  character  of  the  order  Zoantharia,  the  corals 
of  the  present  group  always  show  septa  which  are  some  mul- 
tiple of  five  or  six. 

When  it  is  understood  that  compound  corals,  such  as  we  have  been 
speaking  of,  are  produced  by  the  combined  efforts  of  a  number  of  polypes, 
essentially  the  same  in  structure  as  our  ordinary  sea-anemones,  it  is  readily 
intelligible  that  under  favorable  circumstances  large  masses  of  coral  may  be 
produced  in  this  way.  When  these  masses  attain  such  a  size  as  to  be  of 
geographical  importance,  they  are  spoken  of  as  "  coral-reefs,"  and  the  phe- 
nomena exhibited  by  these  are  of  such  interest  as  to  demand  some  notice. 
The  coral-producing  polypes  require  for  their  existence  that  the  average 


ACTINOZOA. 


89 


temperature  of  the  sea  shall  not  be  less  during  winter  than  66° ;  and  coral- 
reefs  are,  therefore,  not  found  in  temperate  seas.  Keefs,  however,  abound 
in  all  the  seas  not  far  removed  from  the  equator,  being  found  chiefly  on  the 
east  coast  of  Africa  and  the  shores  of  Madagascar,  in  the  Red  Sea  and 
Persian  Gulf,  throughout  the  Indian  Ocean  and  the  whole  of  the  Pacific 
Archipelago,  around  the  West-Indian  Islands,  and  on  the  coast  of  Florida. 
The  headquarters,  however,  of  the  reef-building  corals  may  be  'said  to  be 
around  the  islands  and  continents  of  the  Pacific  Ocean,  where  they  often 
form  masses  of  coral  many  hundreds  of  miles  in  length.  According  to 
Darwin,  coal-reefs  may  be  divided  into  three  principal  forms — viz.,  Fringing- 
reefs,  Barrier-reefs,  and  Atolls,  distinguished  by  the  following  charac- 
ters: 

1.  Fringing-reefs  (Fig.  27,  1). — These  are  reefs,  usually  of  a  moderate 
size,  which  may  either  surround  islands  or  skirt  the  shores  of  continents. 
These  shore-reefs  are  not  separated  from  the  land  by  any  very  deep  channel, 
and  the  sea  on  their  outward  margins  is  not  of  any  great  depth. 

2.  Barrier-reefs  (Fig.  27,  2).  —  These,  like  the  preceding,  may  either 
encircle  islands  or  skirt  continents.     They  are  distinguished  from  fring- 
ing-reefs  by  the  fact  that  they  usually  occur  at  much  greater  distances 
from  the  land,  that  there  intervenes  a  channel  of  deep  water  between  them 
and  the  shore,  and  soundings  taken  close  to  their  seaward  margin  indicate 
great  depths. 


FIG.  27.— Structure  of  Coral-reefs.  1.  Fringing-reef;  2.  Barrier-reef;  8.  Atoll;  a  Sea- 
level ;  &  Coral-reef;  c  Primitive  land ;  d  Portion  of  sea  within  the  reef,  forming  a  chan- 
nel or  lagoon. 


As  an  example  of  this  class  of  reefs  may  be  taken  the  great  barrier-reef 
on  the  northeast  coast  of  Australia,  the  structure  of  which  is  on  a  gigantic  scale. 
This  reef  runs,  with  a  few  trifling  interruptions,  for  a  distance  of  more  than 
a  thousand  miles,  with  an  average  breadth  of  thirty  miles,  and  an  area  of 


90  INVERTEBKATE  ANIMALS. 

thirty-three  thousand  square  miles.  Its  average  distance  from  the  shore  is 
between  twenty  and  thirty  miles,  the  depth  of  the  inner  channel  is  from  ten 
to  sixty  fathoms,  and  the  sea  outside  is  "  profoundly  deep  "  (in  some  places 
over  eighteen  hundred  feet). 

3.  Atolls  (Fig.  27,  3). — These  are  oval  or  circular  reefs  of  coral  enclosing 
a  central  expanse  of  water  or  lagoon.  They  seldom  form  complete  rings, 
the  reef  being  usually  breached  by  one  or  more  openings.  They  agree  in 
all  particulars  with  those  barrier-reefs  which  surround  islands,  except  that 
there  is  no  central  island  in  the  lagoon  which  they  enclose. 

The  last  group  of  the  Zoantharia  comprises  composite  or- 
ganisms in  which  the  ccenosarc  is  supported  upon  a  central 
axis  or  sclerobasic  skeleton.  These  Zoantharia  sclerobasica 
require  no  notice,  except  simply  to  remark  that  they  are  dis- 
tinguished from  other  sclerobasic  corals  (such  as  the  Gor~ 
gonidce)  by  the  fact  that  each  polype  possesses  tentacles  which 
are  a  multiple  of  six  in  number. 

ORDER  II.  ALCYONARIA. — The  second  great  order  of  living 
Actinozoa  is  distinguished  by  the  fact  that  the  polypes  are 
furnished  with  fringed  tentacles,  and  that  these,  as  well  as 
the  mesenteries  and  somatic  chambers,  are  always  some  mul- 
tiple of  four.  With  one  doubtful  exception,  all  the  Al- 
cyonaria  are  composite,  their  polypes  being  connected  to- 
gether by  a  ccenosarc.  The  body-cavities  of  the  polypes  are 
connected  with  a  system  of  canals  which  are  excavated  in  the 
ccenosarc,  and  communicate  freely  with  one  another,  so  that  a 
free  circulation  of  nutrient  fluids  is  thus  kept  up.  The  struct- 
ure of  the  polypes  of  the  Alcyonaria  is,  in  all  essential 
anatomical  features,  the  same  as  in  the  sea-anemones,  the 
number  of  the  mesenteries  and  tentacles  being  the  chief  dis- 
tinction. 

Of  the  various  different  organisms  included  under  this  order, 
one  of  the  best  known  is  the  "  Dead-men's-fingers,"  or  Alcyo- 
niurrij  which  occurs  commonly  in  most  seas.  It  forms  spongy- 
looking  masses  of  a  yellow  or  orange  color,  attached  to  shells 
and  other  marine  objects.  The  whole  mass  is  covered  with 
little  star-shaped  apertures,  through  which  the  delicate  pol- 
ypes can  be  protruded  and  retracted  at  will.  Another  well- 
known  member  of  this  order — the  type  of  another  family — is 
the  "  sea-rod  "  (  Virgularia  mirabilis),  which  occurs  not  very 
rarely  in  shallow  seas.  Virgularia  occurs  in  the  form  of  a  long 
rod-shaped  body  of  a  light  flesh-color,  supported  upon  a  cal- 
careous rod,  somewhat  like  a  knitting-needle,  which  is  covered 
by  the  ccenosarc.  From  the  ccenosarc  are  given  out  lateral 


ACTINOZOA.  91 

processes,  each  of  which  bears  numer- 
ous polypes.  Closely  allied  to  Virgu- 
laria  is  the  "  CockVcomb"  Pennatula 
(Fig.  28) ;  but  in  this  the  lower  end 
of  the  coenosarc  is  naked  and  fleshy, 
and  the  polype -bearing  fringes  are 
considerably  longer,  giving  the  whole 
organism  very  much  the  appearance 
of  a  feather. 

Another  family  of  the  Alcyonaria, 
is  represented  by  the  so-called  "  Or- 
gan-pipe corals,"  of  which  Tubipora 
musica  is  a  well-known  example.  In 
this  there  is  a  well-developed  sclero- 
dermic  coral  consisting  of  numerous 
cylindrical  tubes,  which  are  not  di- 
vided by  vertical  partitions  (septa), 
but  which  are  connected  by  strong 
transverse  plates.  The  coral  is  bright 
red  in  color,  and  the  polypes  are  usually 
bright  green. 

The  best  known,  however,  of  the 
Alcyonaria  is  the  family  Gforgonidce, 
represented  by  the  sea-shrubs,  fan-  FiG.28.-Pennatuiid^TheCock'8- 
corals,  and  the  red  coral  of  commerce.  comb  (Pennatula  phospko- 
A  few  of  the  members  of  this  family 

live  in  temperate  waters,  but  they  attain  their  maximum  in 
point  of  size  and  numbers  in  the  seas  of  the  tropics.  In  all 
the  Gorgonidce  the  organism  consists  of  a  composite  structure 
made  up  of  numerous  polypes  united  by  a  common  flesh  or 
coenosarc  (Fig.  29,  #),  the  whole  supported  by  a  central 
branched  axis  or  coral.  The  coral  varies*  in  composition,  be- 
ing sometimes  calcareous — as  in  red  coral — sometimes  horny, 
and  sometimes  partly  horny  and  partly  calcareous,  as  in  Isis 
(Fig.  29).  In  all  cases,  however,  the  corallum  differs  alto- 
gether from  the  sclerodermic  corallum,  which  has  been  de- 
scribed as  so  characteristic  of  the  reef-building  corals.  The 
coral  in  the  present  instance  is  always  what  is  called  "  sclero- 
basic  " — that  is  to  say,  it  always  forms  an  internal  axis,  covered 
by  the  coenosarc  with  the  polypes  produced  therefrom.  It  is, 
therefore,  outside  the  polypes,  and  bears  to  the  coenosarc  the 
same  relation  that  the  trunk  of  a  tree  bears  to  its  investing 
bark.  This  is  well  shown  in  Fig.  29,  #,  where  there  is  repre- 
sented one  of  these  sclerobasic  corals  in  which  the  corallum 


92 


INVERTEBRATE  ANIMALS. 


consists  of  alternate  horny  and  calcareous  joints.  The  pol- 
ypes of  all  the  GorgonidoB  agree,  of  course,  with  their  order 
in  having  eight  tentacles  each,  and  by  this  they  are  distin- 
guished from  the  few  Zoantharia  in  which  there  is  a  sclero- 
basic  coral. 


FIG.  29.— Sclerodermic  and  Sclerobasic  Corals,  a  Portion  of  branch  of  Dendrophyllia 
nigrescens,  a  sclerodermic  coral  (after  Dana) ;  b  Longitudinal  section  of  Isis  Mppuris, 
a  sclerobasic  coral,  exhibiting  the  external  bark  or  coenosarc,  with  its  imbedded  polypes, 
supported  by  the  internal  axis  or  skeleton  (after  Jones). 


The  best  known  of  the  Gorgonidce  is  the  Corallium  rubrum, 
or  "  red  coral "  of  commerce,  which  is  largely  imported  from 
the  Mediterranean.  In  this  species  there  is  a  bright-red, 
finely-grooved,  calcareous  coral,  usually  more  or  less  repeatedly 
branched.  The  coral  is  invested  by  a  bright-red  coenosarc  or 
bark,  which  is  studded  with  numerous  little  apertures.  The 
polypes  can  be  protruded  from  these  openings  at  will,  and  are 
milk-white  in  color,  with  eight  fringed  tentacles  each.  The 
entire  ccenosarc  is  excavated  into  a  number  of  communicating 
canals,  with  which  the  cavities  of  the  polypes  are  connected, 
the  whole  system  being  filled  with  a  nutritive  fluid  known  as 
the  "milk." 

ORDER  III.  HUGOS  A  (Lat.  rugosus,  wrinkled). — This  order 
merely  requires  mention,  as  all  its  members  are  extinct,  and 
are  therefore  only  known  to  us  by  their  hard  parts  or  skele- 


ACTINOZOA.  93 

tons.  They  agree  with  the  Zoantharia  sclerodermata  in 
having  a  well-developed  sclerodermic  corallum,  but  differ 
from  them  in  the  fact  that  the  septa  are  always  some  multiple 
of  four  /  and  there  are  generally  transverse  plates  or  tabulae 
combined  with  the  vertical  plates  or  septa.  On  the  other 
hand,  they  agree  with  the  Alcyonaria  in  having  their  parts 
in  multiples  of  four,  but  differ  from  them  in  having  a  well- 
developed  sclerodermic  corrallum  in  which  septa  are  present. 

ORDER  IV.  CTENOPHORA  (Gr.  Jcteis,  a  comb;  phero,  I 
carry). — The  fourth  and  last  order  of  the  Actinozoa  is  that  of 
the  Ctenophora,  comprising  a  number  of  free-swimming  oceanic 
creatures,  very  different  in  appearance  from  any  of  the  forms 
which  we  have  hitherto  been  considering.  They  are  all  trans- 
parent, gelatinous,  glassy-looking  creatures,  which  are  found 
near  the  surface  in  the  open  ocean,  swimming  rapidly  by  means 
of  bands  of  cilia.  The  cilia  are  arranged  in  a  series  of  trans- 
verse ridges,  whioh  are  disposed  in  longitudinal  bands,  the 
whole  constituting  locomotive  organs  which  are  known  as 
"  ctenophores."  In  none  are  there  any  traces  of  a  corallum  or 
skeleton,  and  thread-cells  are  asserted  to  be  universally  present. 


FIG.  30.— Ctenophora.    Pltwrobraclda  pileus. 

As  the  type  of  the  order,  we  may  take  one  of  the  commoner 
forms,  which  is  known  by  the  name  of  Pleurobrachia  or  Cy- 
dippe  (Fig.  30).  The  body  of  Pleurobrachia  is  transparent, 
colorless,  gelatinous,  and  melon-shaped,  and  exhibits  two  poles, 
at  one  of  which  is  placed  the  mouth.  The  globe-like  body  is 


94  INVERTEBRATE  ANIMALS. 

divided  into  a  number  of  crescentic  lobes  by  eight  ciliated 
bands  or  ctenophores,  which  proceed  from  near  the  mouth  to 
near  the  opposite  pole  of  the  body.  Besides  the  cilia  there 
are  two  very  long  and  flexible  tentacular  processes,  which  are 
fringed  on  one  side  by  smaller  secondary  branches.  The  ten- 
tacles arise  each  from  a  kind  of  sac,  one  placed  on  each  side 
of  the  body,  and  they  can  be  instantaneously  and  completely 
retracted  within  these  sacs  at  the  will  of  the  animal.  Ihe 
mouth  of  Pleurobrachia  opens  into  a  spindle-shaped  digestive 
sac  or  stomach,  which  in  turn  opens  below  into  a  wider  and 
shorter  cavity  termed  the  "  funnel ; "  from  this  there  proceed 
in  the  axis  of  the  body  two  small  canals,  which  open  at  the 
opposite  pole  of  the  body.  The  funnel  communicates  with  a 
complicated  system  of  canals,  which  are  ciliated  internally, 
and  are  filled  with  a  nutrient  fluid.  In  the  angle  between  the 
two  canals  which  run  from  the  base  of  the  funnel  to  the  sur- 
face is  a  little  vesicle  or  sac,  believed  to  be  a  rudimentary 
organ  of  hearing,  and  placed  upon  this  is  a-  little  mass  which 
is  generally  believed  to  be  of  a  nervous  nature.  If  this  is 
correct,  this  is  the  first  indication  which  we  have  hitherto  en- 
countered of  a  genuine  nervous  system.  The  reproductive 
organs  are  developed  in  the  walls  of  the  canal-system. 

The  only  other  form  of  the  Ctenophora  which  deserves 
mention  is  the  "Venus's  girdle"  (Cesium  Veneris),  which 
agrees  in  essentials  with  Pleurobrachia^  but  is  greatly  enlon- 
gated  in  a  direction  at  right  angles  to  the  alimentary  canal, 
till  we  have  a  ribbon-shaped  body  produced,  four  or  five  feet 
in  length  and  two  or  three  inches  high.  Cestum  is  not  un- 
common in  the  Mediterranean,  and  has  the  power  of  phospho- 
rescence, appearing  at  night  as  a  moving  and  twisting  band 
of  flame. 


SUB  -  KINGD  OM  III.— ANNUL  OIDA. 
CHAPTER  X. 

ECHINODERMATA. 

THE  third  primary  division  of  the  animal  kingdom  is  known 
by  the  name  of  Annuloida,  and  includes  two  groups  of  organ- 
isms which  are  extremely  unlike  one  another  in  appearance, 
and  are  termed  respectively  the  Echinodermata  and  the  Sco- 
lecida.  In  the  former  we  have  the  sea-urchins,  star-fishes,  and 
their  allies,  formerly  classed  in  the  old  sub-kingdom  Radiata ; 
in  the  latter  are  a  number  of  internal  parasites,  with  some 
minute  aquatic  creatures,  all  formerly  referred  elsewhere.  Dif- 
ferent as  are  these  two  groups  in  appearance  and  habits,  they 
are  nevertheless  united  by  the  following  peculiarities :  *  They 
possess  a  distinct  alimentary  canal,  usually  communicating 
with  the  outer  world  by  two  apertures  (a  mouth  and  a  vent),  but 
in  any  case  completely  shut  off  from  the  general  cavity  of  the 
body.  In  all  there  is  a  distinct  nervous  system  ;  and  in  all 
there  is  a  peculiar  system  of  canals  termed  the  "  water-vascu- 
lar "  or  "  aquiferous "  vessels,  which  usually  communicate 
with  the  exterior  of  the  body.  It  should  be  mentioned  that 
many  naturalists  dissent  from  this  grouping  together  of  the 
Echinodermata  and  Scolecida  into  a  single  sub-kingdom, 
Annuloida.  Many  other  arrangements  have  been  proposed, 
most  of  which  present  some  special  advantages  and  some  dis- 
advantages. In  the  mean  while,  in  the  confessedly  uncertain 
state  of  this  department  of  Natural  History,  it  has  been  thought 
well  to  adhere  to  the  arrangement  proposed  by  Prof.  Huxley, 
an  arrangement  with  many  obvious  drawbacks,  and  at  best  but 
provisional. 

*  Some  of  the  internal  parasites  of  this  sub-kingdom  have  no  alimentary  canal  at  all , 
but  this  does  not  affect  the  value  of  the  above  definition. 


90  INVERTEBRATE  ANIMALS. 

CLASS   I. — ECHINODEEMATA. 

The  members  of  this  class  are  popularly  known  as  sea- 
urchins,  star-fishes,  brittle-stars,  feather-stars,  sea-cucumbers, 
etc.,  and  derive  their  name  of  Echinodermata  (Gr.  echinos,  a 
hedgehog ;  and  derma,  skin)  from  the  generally  prickly  nature 
of  their  integuments.  In  all,  the  skin  is  possessed  of  the  power 
of  secreting  carbonate  of  lime,  but  in  very  different  degrees. 
In  the  sea-urchins  this  goes  so  far  that  the  body  becomes  en- 
closed in  an  immovable  box,  composed  of  numerous  calcareous 
plates  firmly  jointed  together.  In  the  star-fishes  and  their 
allies  the  skin  is  rendered  prickly  by  grains,  tubercles,  or 
spines  of  calcareous  matter,  and  the  body  is  either  destitute 
of  regular  plates  or  is  only  partially  enclosed  by  them.  In  the 
sea-cucumbers,  again,  the  calcareous  matter  is  mostly  only 
present  in  the  form  of  minute  grains  scattered  in  the  skin. 
When  adult,  they  all  show  a  more  or  less  distinctly  radiate 
structure,  which  is  most  conspicuous  in  the  star-shaped  star- 
fishes and  sand-stars,  but  can  be  detected  in  all  the  members 
of  the  class.  When  young,  however,  they  almost  always  ex- 
hibit what  is  called  "  bilateral  symmetry  " — that  is  to  say,  they 
show  similar  parts  on  the  two  sides  of  the  body.  In  all  Echino- 
derms  there  is  a  water-vascular  system  of  tubes,  which  is 
termed  the  "ambulacral  system,"  which  generally  communi- 
cates with  the  exterior,  and  which  in  most  cases  is  used  in 
locomotion.  An  alimentary  canal  is  always  present,  and  is 
always  completely  shut  off  from  the  general  cavity  of  the 
body.  A  vascular  or  circulatory  system  is  sometimes  present. 
There  are  always  distinct  organs  of  reproduction,  which  are 
almost  always  placed  in  different  individuals,  so  that  the  sexes 
are  distinct.  The  nervous  system  is  in  the  form  of  a  ring  sur- 
rounding the  gullet  and  sending  branches  in  a  radiating  man- 
ner to  different  parts  of  the  body. 

The  Echinodermata  are  divided  into  seven  orders,  as  fol- 
lows: 

1.  Echinoidea  (Sea-urchins). 

2.  Asteroidea  (Star-fishes). 

3.  Ophiuroidea  (Sand-stars  and  Brittle-stars). 

4.  Crinoidea  (Feather-stars). 

5.  Cystoidea  (extinct). 

6.  JBlastoidea  (extinct). 

7.  Holothuroidea  (Sea-cucumbers). 

This  is  by  no  means  a  true  arrangement  of  these  orders,  but 
it  is  convenient  to  consider  them  in  this  sequence. 


ECHINODEKMATA. 


97 


ORDER  I.  ECHISTOIDEA.— The  animals  included  in  this  order 
vary  from  the  shape  of  a  sphere  or  globe  to  that  of  a  disk,  and 
they  are  all  commonly  known  as  "  sea-urchins  "  or  "  sea-eggs." 
They  are  all  characterized  by  the  fact  that  the  body  is  encased 
in  a  "  test"  or  "shell"  (Fig.  31,  2)  composed  of  numerous  cal- 
careous plates  mostly  immovably  jointed  together  so  as  to  form 
a  kind  of  box.  The  intestine  is  convoluted,  and  there  is  a 
distinct  vent,  or  anal  aperture. 

The  test  of  a  sea-urchin,  as  just  said,  consists  of  many  cal- 
careous plates  accurately  fitted  together,  and  united  by  their 
edges.  In  all  living  forms  the  test  is  composed  of  ten  zones 
of  plates,  each  zone  consisting  of  a  double  row.  In  five  of 
these  zones  (1  a,  2  a)  the  plates  are  of  large  size,  and  are  per- 


FIG.  31.— Morphology  of  Echinoidea.  1.  Portion  of  the  test  of  a  sea-urchin  (Galwites) 
enlarged,  showing  the  ambulacral  areas  (6)  and  interambulacral  areas  (a).  2.  Test  of 
the  same,  viewed  from  above:  a  Interambulacra ;  b  Ambulacra.  8.  Genital  disk  of  a 
sea-urchin  (Hemicidaris)  enlarged:  c  Ocular  plate;  d  Genital  plate :  e  Anal  aperture : 
/Madrcporiform  tubercle.  4.  Spine  of  the  same.  (After  Forbes.) 

forated  by  no  apertures.  These  are  termed  the  "interambu- 
lacral areas."  In  the  other  five  zones  (1  5,  2  t>)  the  plates  are 
of  small  size,  and  are  perforated  by  little  apertures  for  the 
emission  of  delicate  locomotive  suctorial  tubes  (the  so-called 
"ambularcal  tube-feet").  These  zones  are  therefore  called 
the  "  ambulacral  areas."  Besides  these  main  rows  of  plates 
which  collectively  make  up  the  greater  part  of  the  test,  there 
are  other  plates  placed  in  the  leathery  skin  round  the  mouth 
and  vent.  The  most  important  of  these  form  a  kind  of  disk, 
which  is  placed  at  the  summit  of  the  shell.  This  disk  (Fig. 
31,3)  is  composed  of  two  sets  of  plates — one  called  the  "geni- 


98  INVERTEBRATE  ANIMALS. 

tal  plates,"  perforated  for  the  ducts  of  the  reproductive  organs; 
the  other  set  smaller,  and  each  carrying  a  little  "  eye,"  hence 
their  name  of  "  ocular  plates."  One  of  the  genital  plates  is 
also  larger  than  the  others,  and  carries  a  spongy  mass  which 
is  called  the  "  madreporiform  tubercle,"  and  which  protects  the 
entrance  of  the  water-vascular  or  ambulacral  system.  The 
whole  of  the  test  is  covered  with  numerous  tubercles  of  dif- 
ferent sizes,  which  carry  longer  or  shorter  spines  (Fig.  32). 
The  spines  are  jointed  to  the  tubercles  by  a  sort  of  "  ball-and- 


FIG.  32.— Cidaris  papillata  (after  Gossc). 

socket "  or  "  universal "  joint,  and  they  are  completely  under 
the  control  of  the  animal,  so  as  to  be  used  both  in  locomotion 
and  apparently  as  defensive  weapons.  In  most  common  species 
the  spines  are  short,  but  in  many  tropical  forms  they  attain  a 
very  great  length.  Besides  the  spines,  the  outer  surface  of 
the  test  is  furnished  with  curious  little  bodies  called  "  pedi- 
cellariae,"  which  were  long  believed  to  be  parasitic.  They 
consist  of  two  or  three  blades  mounted  upon  a  flexible  stalk 
and  constantly  employed  in  snapping  together  like  the  beak 
of  a  bird.  They  occur  in  many  other  Echinodermata^  and 
their  use  is  obscure. 

Locomotion  is  effected  in  the  sea-urchins  by  a  curious 
system  of  contractile  tubes  which  are  known  as  the  "ambu- 
lacral tubes "  or  "  tube-feet,"  and  which  are  appendages  of 
the  water-vascular  system.  The  following  is  essentially  the 
arrangement  of  the  whole  aquiferous  system.  From  the 
madreporiform  tubercle  on  the  largest  of  the  genital  plates 


ECHINODERMATA.  99 

there  proceeds  a  membranous  canal  by  which  the  outer  water 
is  conducted  to  a  central  tube,  which  forms  a  ring  round 
the  gullet.  The  tubercle  is  spongy,  and  is  perforated  with 
little  holes,  and  its  function  is  probably  to  act  as  a  filter,  and 
prevent  foreign  particles  gaining  access  to  the  interior.  From 
the  "  circular  canal "  round  the  gullet  proceed  five  "  radiating 
canals "  which  take  their  course  toward  the  summit  of  the 
shell,  underneath  the  ambulacral  areas.  In  its  course  each 
radiating  canal  gives  off  numerous  short  lateral  tubes — the 
ambulacral  tubes  or  tube-feet — which  gain  the  exterior  of 
the  shell  by  passing  through  the  apertures  in  the  ambulacral 
plates  of  the  shell,  and  which  terminate  in  little  sucking- 
disks.  The  tube-feet  can  be  distended  with  water  by  means 
of  a  series  of  little  muscular  bladders  placed  at  their  bases, 
and  they  can  thus  be  thrust  far  out  beyond  the  shell,  into 
which  they  can  be  again  withdrawn  at  the  will  of  the  animal. 
However  long  the  spines  may  be,  the  animal  can  protrude 
the  tube-feet  to  a  still  greater  length ;  and  by  the  combined 
action  of  the  little  suckers  at  their  extremities  locomotion  is 
effected  with  moderate  rapidity,  considering  the  bulk  of  the 
body. 

The  digestive  system  in  the  Echinus  consists  of  a  mouth 
armed  with  a  curious  apparatus  of  calcareous  teeth,  which 
opens  into  a  gullet,  which  in  turn  conducts  to  a  distinct 
stomach.  From  the  stomach  there  proceeds  a  long  and  con- 
voluted intestine,  which  is  attached  to  the  interior  of  the 
shell  by  a  delicate  membrane  or  "  mesentery,"  and  terminates 
in  a  distinct  vent.  The  surface  of  the  mesentery,  as  well  as 
that  of  the  lining  membrane  of  the  shell,  is  richly  ciliated,  and 
thus  serves  to  distribute  the  fluids  of  the  body-cavity  to  all 
parts  of  the  body.  In  this  way,  also,  respiration  is  subserved, 
though  it  is  probable  that  the  chief  agent  in  this  function  is 
to  be  found  in  certain  specialized  portions  of  the  ambulacral 
system.  The  circulatory  system  consists  in  its  central  portion 
of  two  rings  placed  round  the  opposite  ends  of  the  alimentary 
canal,  and  united  by  an  intermediate  muscular  cavity  or  heart. 
The  nervous  system  consists  of  a  gangliated  cord  placed  round 
the  gullet,  and  sending  five  radiating  branches  along  the 
ambulacral  areas.  The  sexes  are  distinct,  but  in  both  the  re- 
productive organs  are  in  the  form  of  five  membranous  sacs 
placed  in  a  radiating  manner  in  the  interambulacral  areas,  and 
opening  at  the  genital  plates.  The  embryo  of  the  Echinus  is 
at  first  a  little  free-swimming  ciliated  organism,  and  it  passes 
through  an  extraordinary  development,  which  can  only  be 


100 


INVERTEBRATE  ANIMALS. 


alluded  to  here.  In  its  later  stages  it  was  originally  described 
as  a  distinct  animal  under  the  name  of  "  Pluteus^  In  this 
state  the  larva  is  a  curious,  easel-shaped  body,  with  a  distinct 
alimentary  canal  and  an  internal  calcareous  skeleton,  and  ex- 
hibiting distinct  bilateral  symmetry.  The  remarkable  point, 
however,  about  its  further  development  is,  that  the  young 
Echinus  is  developed  out  of  only  a  portion  of  the  Pluteus,  and 
the  greater  part  of  the  latter,  including  the  skeleton,  is  cast 
away  as  useless. 

The  majority  of  the  sea-urchins  are  found  at  moderate 
depths  in  the  sea,  especially  in  the  neighborhood  of  oyster- 
banks.  Others  spend  their  existence  buried  in  the  sand ;  and 
one  species  excavates  holes  for  itself  in  the  solid  rock,  ap- 
parently by  some  mechanical  action. 

OKDER  II.  ASTEROIDEA  (Gr.  aster,  star;  eidos,  form). — 
As  the  structure  of  the  sea-urchins  may  be  taken  as  embody- 
ing the  most  important  anatomical  peculiarities  of  the  Echino- 
dermata,  and  as  this  has  been  described  at  some  length,  it  will 
not  be  necessary  to  do  more  than  briefly  indicate  the  more 
important  characteristics  of  the  remaining  orders.  In  the 
present  order  are  included  all  the  true  star-fishes,  the  sand- 
stars  and  brittle-stars  being  generally  regarded  as  a  distinct 


FIG.  SS.—Cribetta  oculata  (after  Forbes). 

group.  The  body  in  all  the  Asteroidea  is  more  or  less  ob- 
viously star-shaped  (Fig.  33),  consisting  of  a  central  disk  sur- 
rounded by  five  or  more  lobes  or  arms,  which  radiate  from  the 


ECHINODERMATA.  101 

body,  are  hollow,  and  contain  prolongations  from  the  stomach. 
The  body  is  not  enclosed  in  an  immovable  box  or  test,  as  in 
the  sea-urchins,  but  the  integument  is  of  a  leathery  nature, 
and  is  richly  furnished  with  calcareous  plates,  tubercles,  and 
spines.  The  true  star-fishes  are  distinguished  from  the  nearly 
allied  brittle-stars  ( Ophiuroidea)  by  the  fact  that  the  arms  are 
direct  prolongations  of  the  body,  that  they  contain  prolonga- 
tions of  the  stomach,  and  that  they  are  deeply  grooved  on 
their  under  surfaces  for  the  radiating  vessels  of  the  water- 
vascular  system,  which  are  further  protected  by  a  sort  of  in- 
ternal skeleton.  The  upper  surface  of  the  body  and  arms  is 
richly  furnished  with  calcareous  matter,  in  the  form  of  prickles, 
tubercles,  spines,  and  pedicellarias,  these  last  being  peculiarly- 
modified  spines.  The  upper  surface,  also,  exhibits  the  madre- 
poriform  tubercle  in  the  form  of  a  concentrically-striated  disk 
placed  at  the  angle  between  two  of  the  rays,  and  also  the 
aperture  of  the  anus,  when  this  is  present.  The  mouth  is 
placed  in  the  centre  of  the  lower  surface,  and  is  not  furnished 
with  teeth.  It  leads  by  a  short  gullet  into  a  stomach  which 
usually  terminates  on  the  upper  surface  by  an  anal  aperture ; 
but  this  is  occasionally  wanting.  From  the  stomach  in  all 
the  Asteroidea  proceeds  a  series  of  much-branched  membra- 
nous sacs,  two  of  which  are  prolonged  into  each  ray.  The 
water-vascular  or  ambulacral  system  is  in  most  essential  re- 
spects identical  in  structure  with  that  of  the  sea-urchins, 
making  due  allowance  for  the  different  shape  of  the  body. 
The  nervous  system  consists  of  a  gangliated  ring  surrounding 
the  mouth  and  sending  branches  along  each  of  the  arms.  The 
reproductive  organs,  like  the  nervous  system,  exhibit  a  radiate 
condition,  being  arranged  in  pairs  in  each  ray. 

The  star-fishes  are  found  on  all  shores,  but  many  forms  are 
properly  inhabitants  of  deep  water.  They 'differ  much  in  the 
general  shape  of  the  body.  In  the  common  cross-fish  ( Ur aster 
rubens)  the  disk  is  small,  and  is  furnished  with  long,  finger-like 
rays,  which  are  properly  five  in  number.  In  the  Cribettce  (Fig. 
33)  the  general  shape  is  much  the  same.  In  the  sun-stars 
(Solaster)  the  disk  is  large  and  well  marked,  the  rays  are  from 
twelve  to  fifteen  in  number,  and  they  are  shorter  than  the 
diameter  of  the  disk.  In  the  cushion-stars  (Goniaster)  the 
body  is  in  the  form  of  a  five-angled  disk,  more  or  less  flattened 
on  both  sides,  the  rays  being  only  marked  out  by  the  ambula- 
cral grooves  upon  the  lower  surface. 

OKDEK  HI.  OPHIUROIDEA  (Gr.  ophis,  snake;  our  a,  tail;  ei- 


102 


INVERTEBRATE  ANIMALS. 


dosy  form). — In  this  order  we  have  only  the  common  sand-stars 
(  Ophiurd)  and  brittle-stars  ( Ophiocoma),  all  closely  allied  to 
the  true  star-fishes  in  external  appearance,  especially  in  their 
strikingly  radiate  form.  The  body  in  the  Ophiuridce  consists 
of  a  circular  central  disk  covered  with  small  calcareous  plates, 
and  giving  off  five  long,  slender,  snake-like  arms  (Fig.  34,  «,  b), 
which  may  be  simple  or  branched,  but  which  do  not  contain 
any  prolongations  from  the  stomach,  nor  have  their  under 
surfaces  excavated  into  grooves  for  the  protrusion  of  ambu- 
lacral  tube-feet.  The  arms,  in  fact,  are  not  prolongations  or 
lobes  derived  from  the  body  itself,  but  are  special  appendages 
added  for  purposes  of  locomotion  and  prehension.  The  arms 


Fio.  84.— Ophiuroidea.    a  Ophiivra  texturata,  the  common  sand-star;   I  Ophiocoma 
neylecta,  the  gray  brittle-star  (after  Forbes). 


are  very  much  longer  than  the  diameter  of  the  disk,  and  are 
protected  by  four  rows  of  calcareous  plates — one  above,  one 
below,  and  one  on  each  side.  In  the  centre  of  each  arm  is  a 
row  of  calcareous  pieces  which  form  a  kind  of  internal  axis 


ECHINODERMATA. 


103 


or  skeleton,  below  which  is  placed  the  radiating  ambulacral 
vessel.  All  the  internal  organs  are  contained  within  the  disk, 
and  none  of  them  pass  into  the  arms  except  the  nerve-cords 
and  ambulacral  vessels.  The  mouth  is  placed  in  the  centre 
of  the  under  surface  of  the  disk,  and  opens  into  a  globular, 
simple  stomach,  which  is  not  furnished  with  an  anal  aperture, 
all  indigestible  particles  being  got  rid  of  through  the  mouth. 
In  various  points  of  their  anatomy  the  Ophiuroidea  differ 
considerably  from  the  true  star-fishes,  to  which  they  are  most 
nearly  related,  but  these  differences  do  not  require  further 
notice. 

The  habits  of  the  brittle-stars  and  sand-stars  are  various, 
but  many  of  them  may  be  found  in  rock-pools  or  under  stones 
at  low  water  on  most  shores. 


FIG.  35. — Comatula  rosacea.    a  Free  adult ;  &  Fixed  young  (after  Forbes). 

ORDER  IV.  CRINOIDEA  (Gr.  Jcrinos,  a  lily ;  eidos,  form). — 
Tn  this  order  are  comprised  Echinodermata,  in  which  the 
body  is  fixed,  during  the  whole  or  a  portion  of  the  existence 
of  the  animal,  to  submarine  objects  by  means  of  a  jointed 
flexible  stalk  or  column.  The  Crinoidea  were  formerly  very 


104 


INVERTEBRATE  ANIMALS. 


numerous,  both  individually  and  in  types,  but  they  are  rep- 
resented at  the  present  day  by  no  more  than  three  or  four 

living  forms,  of  which  one 
only  (the  feather-star)  is  at 
all  of  common  occurrence. 
The  body  in  the  Crinoids  con- 
sists of  a  central  disk  or  cup 
formed  of  calcareous  plates, 
and  protecting  the  body  of 
the  animal.  From  the  mar- 
gins of  this  cup  spring  five 
or  more  arms -which  are  ar- 
ranged in  a  radiating  manner, 
so  as  to  form  a  more  or  less 
feathery  crown.  In  one  of 
our  living  forms,  the  animal, 
when  full  grown,  is  free ;  but 
in  all  other  living  genera,  and 
in  the  great  majority  of  fossil 
forms,  the  body  was  attached 
throughout  life  to  the  sea- 
bottom  by  means  of  a  jointed 
stalk  attached  to  the  lower 
surface  of  the  cup  (Fig.  36), 
thus  somewhat  resembling  a 
lily. 

The  commonest  living  spe- 
cies is  the  rosy  feather-star 
( Comatula  rosacea\  which 
occurs  not  very  rarely  on 
European  coasts  (Fig.  35). 
This  beautiful  animal  consists 
of  a  central  body  or  disk, 
from  which  proceed  five  ra- 
diating  arms,  which  divide 
almost  directly  after  their 
FIG.  B&.—iikisocrinus  lofotmsis,  a  living  origin  into  two  secondary 

stalked  Crinoid  (after  Wyville  Thomson),  KrnnOV,p>q    on    fhnf    nltirrm+^lv 
four  times  the  natural  size,    a  Stem ;  b   D  es>  sc  imateiy 

Cup;  cc  Arms.  there  are  produced  ten  long 

and  slender  rays.     Each  arm 

is  furnished  on  both  sides  with  a  number  of  little  jointed 
lateral  processes  or  "  pinnae,"  so  as  to  assume  a  feather-like 
appearance,  from  which  its  popular  name  is  derived.  The 
digestive  system  is  furnished  with  both  a  mouth  and  a  vent ; 


ECHINODERMATA. 


105 


the  water-vascular  or  ambulacral  system  appears  to  take  no 
part  in  locomotion,  and  the  reproductive  organs  are  lodged  in 
the  lateral  processes  of  the  arms.  The  most  remarkable  point, 
however,  about  the  Comatula  is  the  manner  in  which  it  de- 
velops itself.  When  fully  grown  (Fig.  35,  a)  it  presents  no 
small  superficial  resemblance  to  some  of  the  Ophiuroidea. 
When  young  (Fig.  35,  b)  the  Comatula  is  so  different  in  ap- 
pearance from  the  adult,  that  it  was  originally  described  as  a 
distinct  animal.  It  consists  now  of  a  little  cup-shaped  disk 
with  ten  radiating  arms  above,  produced  by  the  splitting  into 
two  of  five  primary  rays,  and  furnished  inferiorly  with  a  little 
flexible  column  or  stalk  composed  of  a  number  of  calcareous 
joints.  By  this  jointed  stem  the  body  is  at  this  period  of 
life  fixed  to  sea-weeds  or  other  submarine  objects.  When 
sufficiently  mature,  however,  the  body  drops  off  its  stalk,  and 
then  only  requires  to  grow  in  size  to  become  a  fully-developed 
Comatula. 

The  stalked  condition  which  we  have  just  seen  to  consti- 
tute a  merely  temporary  stage  in  the  life-history  of  the  Coma- 
tula is,  on  the  other  hand,  the  permanent  state  of  parts  in 
almost  all  the  "  stone-lilies  "  and  other  fossil  Crinoidea,  and 
in  two  or  three  living  forms.  Of  these  recent  species,  one  of 
the  most  remarkable  is  one  which  has  been  recently  discovered 
in  the  Atlantic  and  North  Seas,  and  which  has  been  described 
under  the  name  of  Mhizocrinus  lofotensis.  This  curious  species 
(Fig.  36)  consists  of  a  little  thread-like,  jointed  stem  support- 
ing a  calcareous  cup,  from  which  proceed 
five  branched  and  jointed  arms ;  and  the 
stalked  condition  is  here  permanently  re- 
tained during  life. 

ORDERS  V.  AND  VI.  CTSTOIDEA  AND 
BLASTOIDEA. — These  orders  merely  require 
to  be  mentioned  here,  as  all  the  forms  in- 
cluded in  them  are  extinct,  and  are  unrep- 
resented at  the  present  day  by  living  spe- 
cies. In  both,  the  body  is  enclosed  in  a 
kind  of  box  formed  by  jointed  calcareous 
plates  (Fig.  37),  and  it  was  in  most  cases 
permanently  fixed  to  the  sea-bottom  by  a 
jointed  stalk  or  column.  The  arms,  which 
form  so  conspicuous  a  feature  in  the  true  Crinoidea,  were 
either  absent  or  very  rudimentary.  Both  orders  are  most 
closely  allied  to  the  Crinoidea,  and  they  constitute  probably 


FIG.  37.— Cystoidea. 
EcMnosphwrites. 


106  INVERTEBRATE  ANIMALS. 

the  least  highly-developed  sections  of  the  whole  class  of  the 
Echinodermata. 

ORDER  VII.  HOLOTHUROIDEA. — In  this  order  are  comprised 
the  highest  of  the  Ediinodermata,  all  very  different  in  out- 
ward appearance  from  any  of  the  forms  we  have  hitherto  con- 
sidered. They  are  commonly  known  as  sea-cucumbers,  or  tre- 
pangs,  but  they  are  mostly  rare  and  inconspicuous  animals  at 
the  best.  They  are  all  more  or  less  worm-shaped  or  snail-like 
in  form,  and  they  are  either  altogether  destitute  of  calcareous 
matter  in  the  skin,  or  with  rare  exceptions  have  only  scattered 
grains  and  spines  of  this  material.  As  a  rule,  the  skin  is 
simply  leathery,  and  is  endowed  with  wonderful  contractility 
by  means  of  powerful  longitudinal  and  transverse  muscles. 
In  consequence  of  this,  they  can,  in  many  cases,  eject  all  or 
almost  all  their  internal  organs,  and  can  sometimes  divide  their 
bodies  into  several  parts  when-  injured  or  alarmed.  Loco- 
motion is  effected  by  alternate  extension  or  contraction  of  their 
worm-like  bodies,  by  anchor-shaped  spicules  of  lime  contained 
in  the  skin,  or  by  rows  of  ambulacral  tube-feet,  like  those  of 
the  sea-urchins,  protruded  through  the  integument.  Some- 
times the  tube-feet  are  scattered  over  the  whole  surface  of  the 
body,  and  sometimes  they  are  altogether  absent.  There  is 
always  a  mouth  at  one  extremity  of  the  body,  and  a  distinct 
vent  at  the  other.  The  mouth  is  situated  anteriorly,  and  is 
surrounded  by  a  circlet  of  feathery  tentacles  (Fig.  38),  which 


FIG.  3S.— Holothuroidea.     Thyone  papillosa  (after  Forbes). 


are  believed  to  be  modified  tube-feet.  The  water-vascular  or 
ambulacral  system  is  sometimes  quite  rudimentary,  but  in 
other  cases  it  much  resembles  that  of  the  sea-urchins,  except 
that  the  madreporiform  tubercle  is  not  placed  on  the  outside 
of  the  body,  but  hangs  down  freely  in  the  interior  of  the  body. 
In  most  of  the  Holothuroidea  there  are  appended  to  the  ter- 
mination of  the  intestinal  canal  two  much-branched  tubes, 


ECHINODERMATA.  107 

which  are  filled  with  sea-water  from  without,  and  are  believed 
to  exercise  a  respiratory  function,  hence  the  name  of  "  respi- 
ratory tree  "  often  applied  to  them. 

The  ordinary  species  of  Holothurians,  as  already  said,  are 
all  rare,  and  are  mostly  only  to  be  obtained  by  dredging  in 
tolerably  deep  water.  Some  of  the  tropical  forms  attain  a 
large  size,  and  some  are  largely  searched  after  to  be  sold  in  the 
Chinese  market,  being  regarded  in  that  country  as  a  delicacye 


CHAPTER  XL 
CLASS  II — SCOLECIDA. 

IN  the  second  class  of  the  sub-kingdom  Annuloida  are  in- 
cluded a  number  of  organisms  which  are,  in  many  cases,  very 
unlike  one  another  in  external  appearance,  but  which,  never- 
theless, agree  in  one  or  two  structural  points  of  importance. 
The  most  important  of  these  are  the  possession  of  a  system 
of  water- vascular  ves^sels^the  absence  of  a  vascular  system, 
and  the  possession  of  a  nervous  system  composed  of  no  more 
than  one  or  two  nervous  masses  or  ganglia.  The  points  by 
which  the  Scolecida  are  distinguished  from  the  Echinodermata 
are,  the  absence  of  calcareous  matter  in  the  skin,  the  absence 
of  any  traces  of  a  radiate  arrangement  of  their  parts,  especially 
of  the  nervous  system,  the  constant  absence  of  any  blood- 
circulatory  apparatus,  and  the  course  of  their  development. 
The  Scolecida  (Gr.  skolex,  a  worm)  are  often  vermiform  in 
shape,  but  many  of  them  exhibit  no  worm-like  characters, 
and  one  whole  order  is  entirely  microscopic.  A  great  many 
of  the  Scolecida  are  internal  parasites  in  other  animals,  and 
these  are  often  collectively  spoken  of  as  JEJntozoa  (Gr.  entos, 
within ;  zoon,  an  animal).  These  parasitic  forms  subsist  by 
an  imbibition  of  the  juices  of  their  host  through  their 
delicate  integument.  They  have,  therefore,  no  necessity  for 
acquiring  food  for  themselves ;  and  we  find,  in  consequence, 
that  many  of  them  are  wholly  destitute  of  an  alimentary 
canal,  and  that  in  all  the  organs  of  "  relation  "  are  very  rudi- 
mentary. The  /Scolecida  are  divided  into  the  following  seven 
groups  or  orders : 

1.  Tceniada  (Tape- worms). 

2.  Trematoda  (Flukes). 

3.  Turbellaria  (Ribbon-worms  and  Planarians). 


SCOLECIDA.  109 

4.  Acanthocephala  (Thorn-headed  worms). 

5.  G-ordiacea  (Hair-worms). 

6.  Nematoda  (Round-worms  and  Thread- worms). 

7.  Rotifer  a  (Wheel-animalcules). 

ORDER  I.  T^EOTADA  (Gr.  tainia,  a  ribbon). — In  this  order 
are  comprised  the  ribbon-shaped  Tape-worms  (Fig.  39,  5)  and 


FIG.  39. — Morphology  of  Taeniada.  1.  Ovum  containing  the  embryo  in  its  leathery  case; 
2.  A  bladder-worm  (Cysticercus  longicollis),  magnified ;  3.  Head  of  the  adult  Tomia 
soliwm,  enlarged,  showing  the  suckers  and  crown  of  booklets ;  4.  A  single  generative 
joint,  enlarged  to  show  the  branched  ovary  (o),  the  generative  pore  (a),  and  the  water- 
vascular  canals  (6) ;  5.  Fragment  of  Toenia  solium,  showing  the  generative  joints  and 
the  alternate  arrangement  of  the  generative  pores. 

the  bladder-worms  or  cystic  worms  (Fig.  39,  2).  These  were 
formerly  described  as  distinct  groups ;  but  it  is  now  known 
that  the  latter  are  merely  the  young  forms  of  the  former.  The 
peculiarity  which  distinguishes  the  development  of  the  Tceni- 
ada,  and  which  led  to  the  cystic  worms  being  described  as 
distinct  animals,  is  that  the  different  stages  of  growth  are 
always  found  inhabiting  different  animals  or  "  hosts."  If  the 
fully-grown  tape- worm  is  found  in  one  animal,  then  its  young 
form  or  cystic  worm  will  always  be  found  in  another.  Many 
animals  are  infested  by  tape-worms ;  but  all  the  leading  points 
of  interest  in  the  order  will  be  brought  out  by  a  consideration 
of  the  commonest  of  the  three  tape-worms  to  which  man  is 
subject — namely,  the  common  tape-worm,  or  Tcenia  solium. 

6 


110  INVERTEBRATE  ANIMALS. 

The  common  tape-worm  is  found  inhabiting  the  intestines  of 
man,  one  only  being  generally  present  in  the  same  individual. 
In  shape  (Fig.  39,  5)  it  is  an  extremely  elongated,  flattened, 
tape-like  body,  many  feet  in  length,  and  composed  of  a  num- 
ber of  flattened  joints  (Fig.  39,  4)  all  loosely  united  to  one 
another.  At  one  extremity  the  joints  become  much  smaller 
and  narrower,  till  ultimately  a  point  is  reached  where  the 
organism  is  firmly  fixed  to  the  mucous  membrane  of  the  in- 
testine by  means  of  a  minute  rounded  head  (Fig.  39,  3). 
The  organs  by  which  attachment  is  effected  are,  in  this  spe- 
cies, a  crown  of  recurved  hooks  and  four  suckers.  The  head 
is  in  reality  the  true  animal,  and  all  the  long,  jointed,  tape- 
like  body  which  follows  this,  is  really  produced  by  a  process 
of  budding  from  the  head.  The  head  contains  no  repro- 
ductive organs,  and  is  not  furnished  with  a  mouth  or  diges- 
tive organs  of  any  kind,  its  nutrition  being  entirely  effected 
by  imbibition  of  the  nutritive  fluids  elaborated  by  its  host.  A 
nervous  system,  in  the  form  of  one  or  two  ganglia,  sending 
filaments  backward,  is  said  to  be  present ;  but  there  is  some 
doubt  on  this  point.  The  water-vascular  system  (Fig.  39,  4) 
consists  of  two  long  vessels  which  run  down  each  side  of  the 
body  and  communicate  at  each  articulation  by  a  transverse 
vessel,  the  whole  opening  in  the  last  joint  into  a  contractile 
vesicle.  Each  joint  is  sexually  perfect,  or  hermaphrodite, 
containing  both  male  and  female  reproductive  organs  (Fig. 
39,  4),  which  open  on  the  surface  by  a  small  raised  aperture, 
the  "generative  pore."  Almost  the  whole  of  each  of  the 
mature  joints  is  filled  up  by  a  much-branched  ovary.  As  the 
head  is  the  true  animal,  and  the  numerous  joints  are  only  pro- 
duced by  budding,  it  follows  that  the  entire  organism  is  to  be 
regarded  as  a  kind  of  colony,  constituted  by  a  single  sexless 
zoo"id  or  "  nurse,"  and  numerous  sexual  zooids,  produced  by 
budding  from  the  former. 

The  process  of  development — that  is  to  say,  the  process 
by  which  this  composite  organism,  commonly  known  as  the 
tape-worm,  is  produced — is  a  very  remarkable  one,  and  is 
briefly  as  follows:  Each  generative  segment  or  joint,  as  al- 
ready said,  is  hermaphrodite,  and  contains  innumerable  ova. 
These  eggs,  however,  cannot  be  developed  within  the  body 
of  the  animal  infested  by  the  tape-worm  itself,  but  they  are 
compelled  to  gain  access  to  the  body  of  some  different  species 
of  animal,  if  development  is  to  proceed.  To  secure  this  end, 
the  mature  joints  of  the  colony  break  off,  and  are  expelled 
from  the  alimentary  canal  of  the  host.  The  joints  thus  ex- 


SCOLECIDA.  HI 

pelled  die  and  decompose,  and  their  contained  eggs  are  thus 
set  free.  Each  egg  (Fig.  39, 1)  is  covered  with  a  little  leathery 
capsule  which  protects  it  from  injury,  and  contains  a  minute 
embryo  in  its  interior.  If  this  microscopically  small  egg  be 
swallowed — as  in  many  ways  it  easily  may  be — by  another 
warm-blooded  animal  (in  this  particular  case  by  the  pig), 
then  a  fresh  series  of  changes  ensues.  The  leathery  case  of 
the  ovum  is  dissolved  in  the  stomach  of  the  new  host,  and 
the  embryo  is  set  free,  when  it  bores  its  way  through  the 
walls  of  the  stomach  by  means  of  little  siliceous  hooks  with 
which  it  is  provided.  Having  reached  a  suitable  locality,  the 
young  tape-worm  proceeds  to  surround  itself  with  a  kind  of 
cyst,  and  it  develops  from  its  hinder  end  a  kind  of  bladder 
filled  with  fluid  (Fig.  39,  2).  It  is  now  a  bladder-worm,  or 
cystic  worm,  and  as  such  would  formerly  have  been  regarded 
as  a  distinct  animal.  In  the  particular  case  of  the  Tcenia 
solium  which  we  are  now  considering,  the  cystic  worm  is 
found  imbedded  in  the  muscles  of  the  pig,  and  it  constitutes 
in  that  animal  the  disease  known  as  the  measles.  In  this 
cystic  stage  the  young  tape-woim  rnay  remain  for  an  ap- 
parently indefinite  period,  being  quite  incapable  of  develop- 
ing eggs,  though  sometimes  fresh  bladder-worms  may  be 
produced  by  a  process  of  budding.  For  its  further  develop- 
ment it  is  necessary  that  it  should  now  be  introduced  into 
the  alimentary  canal  of  man.  If  a  portion  of  measly  pork  be 
eaten  with  these  cystic  worms  imbedded  in  it,  then  the 
young  tape-worm  is  liberated  from  its  cyst:  it  fixes  itself 
by  means  of  its  suckers  and  booklets  to  the  mucous  mem- 
brane of  the  intestine,  and  its  caudal  bladder  drops  off.  It  is 
now  converted  into  the  head  of  the  adult  tape-worm.  It 
finally  commences  to  throw  out  buds  from  its  hinder  extremity, 
and  in  these  buds  or  joints  the  reproductive  elements  are  pro- 
duced, so  that  ultimately  we  get  the  long,  flattened  jointed 
colony  with  which  we  started. 

This  extraordinary  series  of  phenomena  is  now  known  to 
occur  in  other  cases,  but  space  will  not  admit  our  dwelling 
upon  these.  Another  of  the  tape-worms  of  man  (the  Tcenia 
mediocanellatd)  is  developed  in  the  same  way  from  the 
measles  of  the  ox.  The  tape-worm  of  the  cat  is  the  mature 
form  of  the  bladder- worm  of  mice,  and  the  tape- worm  of  the  fox 
is  derived  from  the  cystic  worm  of  hares  and  rabbits.  Lastly, 
man  is  not  only  liable  to  be  infested  with  the  tape-worms 
derived  from  the  cystic  worms  of  other  animals,  but  may  be 
attacked  by  the  cystic  or  immature  forms  of  the  tape-worms 


112 


INVERTEBRATE  ANIMALS. 


of  other  animals.  Thus  the  disease  known  as  "  hydatids  "  in 
the  human  subject  is  caused  by  the  presence  in  his  tissues  of 
the  cystic  worms  which  are  ultimately  developed  into  the  tape- 
worm of  the  dog. 

ORDER  II.  TREMATODA  (Gr.  trema,  a  pore  or  sucker). — 
The  "  suctorial "  worms,  or  "  flukes,"  as  the  members  of  this 
order  are  commonly  called,  are  all  internal  parasites,  inhabit- 
ing various  situations  in  different  animals,  but  especially  af- 
fecting birds  and  fishes.  They  are  all  more  or  less  flattened 
and  rounded  in  shape,  and  are  furnished  with  one  or  more 
suckers,  by  which  they  adhere.  They  are  distinguished  from 
the  Tceniada  by  always  possessing  an  alimentary  canal,  which 
is  often  much  branched  (Fig.  40,  1),  is  simply  hollowed  out 


FIG.  40.— Trematoda.  1.  Distoma  hepaticum,  the  "liver-fluke,"  showing  the  branched 
alimentary  canal :  2.  Anterior  extremity  of  Distoma  lanceolatum,  enlarged ;  a  An- 
terior sucker ;  b  Posterior  sucker ;  o  Generative  pore ;  d  Gullet ;  e  e  Bifurcating  aliment- 
ary canal  (after  Owen). 


of  the  tissues  of  the  body,  and  is  never  provided  with  a  dis- 
tinct anus.  The  best  known  of  the  Trematoda  is  the  common 
liver-fluke  (Distoma  hepaticum,  Fig.  40,  1),  which  inhabits 
the  gall-bladder  or  ducts  of  the  liver  in  sheep,  and  is  the  cause 
of  the  disease  known  as  the  rot.  In  form  it  is  ovate,  flat- 
tened on  the  two  sides,  and  presenting  two  suckers,  of  which 
the  anterior  is  perforated  by  the  aperture  of  the  mouth.  A 
branched  water-vascular  system  is  present,  and  opens  pos- 
teriorly by  a  small  aperture.  The  alimentary  canal  bifurcates 
shortly  behind  the  mouth,  the  two  divisions  thus  produced 
being  much  branched,  and  terminating  posteriorly  in  blind 
extremities.  In  Distoma  lanceolatum  (Fig.  40,  2)  the  intes- 
tine is  divided  into  two  branches,  but  these  are  simple  tubes, 
and  are  not  branched. 


SCOLECIDA. 


113 


OKDER  HI.  TURBELLARIA. — The  animals  included  in  this 
order  differ  altogether  from  the  Trematoda  and  Tceniada  in 
being-  almost  all  aquatic  in  their  habits  and  being  all  non- 
parasitic.  They  never  possess  sucking-disks  or  booklets,  and 
their  integument  is  always  furnished  with  vibrating  cilia.  A 
water-vascular  system  is  always  present,  but  it  appears  some- 
times not  to  communicate  with  the  exterior.  The  alimentary 
canal  is  sometimes  simply  hollowed  out  of  the  tissues  and 
destitute  of  an  anus,  as  in  the  Trematoda,  or  at  other  times 
suspended  in  a  free  space  (body-cavity)  and  furnished  with  an 
anus.  It  may  be  simple  or  much  branched. 

The  best  known  of  the  members  of  this  order  are  certain 
little  jelly-like,  soft-bodied,  ovate,  or  elliptical  creatures,  which 
are  commonly  found  in  fresh  water  or  on  the  sea-shore,  and  are 
known  as  Planarians.  The  skin  in  these  curious  little  ani- 
mals (Fig.  41,  1,  2)  is  richly  furnished  with  cilia,  and  also 
contains  numerous  cells  which  have  been  compared  to  the 


FIG.  41. — Turbellaria.  1.  Planaria  torva:  m  Mouth;  (7  Nerve-ganglion ;  e  Eyes;  ov 
Ovary;  t  Spermarium ;  gn  Genital  opening:  2.  Planaria,  lactea,  showing  the  branched 
intestine:  3.  Larva  of  one  of  the  marine  Turbellarians :  4.  Pilidium,  the  larva  of  one 
of  the  Nemertidm. 


"nettle-cells"  of  the  Ccelenterata.  The  intestine  may  be 
either  straight  or  branched,  but  always  terminates  behind 
in  blind  pouches,  and  is  never  provided  with  an  anus.  The 
water-vascular  system  communicates  with  the  exterior.  The 
nervous  system  consists  of  two  ganglia,  placed  in  front  of  the 
mouth,  and  united  by  a  cord.  There  are  generally  rudimen- 
tary eyes  or  pigment-spots,  which  vary  in  number  from  two 
to  sixteen. 

The  remaining  members  of  the  Turbellaria  are  known  as 
ribbon-worms  (Nemertidve),  and  are  not  uncommonly  found 
on  the  sea-shore.  They  differ  from  the  Planarida  in  beinpf 


114  INVERTEBRATE  ANIMALS. 

worm-like  in  shape,  by  the  fact  that  the  alimentary  canal  is 
furnished  with  a  distinct  anus,  and  by  the  absence  of  an  ex- 
ternal opening  to  the  water- vascular  system  of  the  adult,  in 
some  cases  at  any  rate.  Their  development  sometimes  shows 
phenomena  very  similar  to  what  occurs  in  the  Echinodermata, 
the  larva  (Fig.  41,  4)  being  a  free-swimming,  ciliated  organ- 
ism, of  which  only  a  portion  is  employed  in  producing  the 
adult  animal,  the  remainder  being  cast  off  as  useless. 

OEDER  IV.  ACANTHOCEPHALA  (Gr.  aJcantha,  thorn ;  Tee- 
phale,  head). — The  "thorn-headed  worms"  included  in  this 
order  are  all  internal  parasites.  They  are  worm-like  in  shape, 
marked  with  transverse  wrinkles,  and  destitute  of  any  mouth 
or  alimentary  canal.  The  anterior  extremity  of  the  body  forms 
a  kind  of  proboscis  or  snout,  which  is  armed  with  recurved 
hooks,  and  has  placed  at  its  base  a  single  nervous  ganglion. 
Beneath  the  skin  is  a  net-work  of  canals,  containing  a  clear 
fluid,  and  believed  to  represent  the  water-vascular  system. 
The  thorn-headed  worms  include  some  of  the  most  formidable 
parasites  with  which  we  are  as  yet  acquainted,  the  best  known 
being  the  various  forms  of  JSchinorhynchus,  which  are  found 
inhabiting  the  alimentary  canal  in  many  mammals,  birds,  and 
fishes,  but  not  as  yet  in  man. 

ORDER  V.  GORDIACEA. — The  Gordiacea,  or  "hair-worms," 
are  thread-like  parasites  which  in  the  earlier  stages  of  their 
existence  inhabit  the  bodies  of  various  insects,  chiefly  beetles 
and  grasshoppers.  They  possess  a  mouth  and  alimentary 
canal.  The  sexes  are  distinct,  and  they  leave  the  bodies  of 
the  insects  which  they  infest  to  breed,  subsequently  deposit- 
ing their  eggs  in  long  chains  either  in  water  or  in  some  moist 
situation.  In  form  the  Gordiacea  are  singularly  like  hairs,  and 
they  often  attain  a  length  very  many  times  greater  than  that 
of  the  insect  in  which  they  live. 

ORDER  VI.  NEMATODA  (Gr.  nema,  a  thread). — In  this 
order  are  the  "  round-worms  "  and  "  thread-worms,"  both  of 
which  are  parasitic,  together  with  a  number  of  worms  which 
lead  a  permanently  free  existence.  All  the  Nematoda  (Fig. 
42)  are  elongated  and  cylindrical  or  thread-like  in  shape. 
They  possess  a  distinct  mouth,  and  an  alimentary  canal  which 
is  freely  suspended  in  an  abdominal  cavity,  and  which  termi- 
nates in  a  distinct  anus.  They  possess  a  system  of  canals 
which  are  believed  to  represent  the  water-vascular  system ; 


SCOLECIDA. 


115 


and  the  nervous  system  is  in  the  form  of  a  gangliated  cord 

surrounding   the   gullet,   and    sending    filaments   backward. 

Among  the  best  known  of  the  parasitic  Nematodes  are  the 

common  round-worm  (Ascaris  lumbricoides)  and  the  thread- 

worm (  Oxyuris)  of  the  human  subject,  both  of  which  inhabit 

the  alimentary  canal,  and  the  guinea-  worm  (Filarid),  which 

spends  a  portion  of  its  existence  in 

the  cellular  tissue  of  man,  especially 

of  the  legs,  and   which  attains  a 

length  of  several  feet.     More  dan- 

gerous  than  any  of  these    is   the 

Trichina,  which  spends  its  immature 

stages  encysted  in  the  muscles  of 

some  such  animal  as  the  pig,  and 

only  attains  maturity  and  becomes 

capable  of  producing  eggs,  when  in- 

troduced into  the  alimentary  canal 

of  some  other  warm-blooded  verte- 

brate   animal.     When    this    takes 

place,   a   train   of    symptoms    are 

originated    which     sometimes    re- 

semble rheumatic  fever,  and  appear 

to  be  very  generally  fatal. 

Of  the  free  Nematode  worms, 
which  are  never  parasitic  at  any 
time  of  their  lives,  about  two  hun- 
dred species  have  been  described, 
most  of  which  inhabit  fresh  water 
or  the  shores  of  the  sea.  One  of 
the  most  familiar  is  the  so-called 
"  vinegar  -  eel  "  (Anguillula  acetL 
Fig.  42,  A). 

FIG.  42.  —  Nomatoda.    A.  Vinegar-eel 


OBDEE  Vin.    ROOTERA  (Lat. 

rota,  wheel;  jero,  I  carry).  —  The       living  in  stagnant  water. 
Rotifera,  or  "wheel-animalcules," 

derive  their  popular  name  from  the  fact  that  the  anterior  end 
of  the  body  is  furnished  with  one  or  two  circlets  of  cilia 
(Fig.  43)  which,  when  in  motion,  vibrate  so  rapidly  as  to 
produce  the  illusory  impression  of  a  quickly-rotating  toothed 
wheel.  The  Rotifera  are  almost  all  aquatic,  and  are  mostly 
inhabitants  of  fresh  water.  They  are  all  microscopic  in  size, 
none  attaining  a  greater  length  than  one-thirty-sixth  of  an  inch. 
In  the  females  there  is  a  distinct  mouth,  intestinal  canal,  and 


116 


INVERTEBRATE  ANIMALS. 


anus.  A  nervous  system  is  also  present,  consisting  of  gan- 
glia placed  near  the  anterior  extremity  of  the  body  and  send- 
ing filaments  backward.  There  is,  finally,  a  well-developed 
water-vascular  system. 

Most  of  the  Hotifera  are  free-swimming,  active  little  ani- 
mals (Fig.  43,  A),  but  some  are  permanently  fixed,  as  in 
Melicerta  (Fig.  43,  B),  or  in  the  crown-animalcule  Stephano- 
ceros).  They  are  usually  simple,  but  they  are  sometimes  com- 
posite, forming  colonies.  As  a  rule,  the  male  and  female 
Hotifera  differ  greatly  from  one  another,  the  males  being 
smaller  than  the  females,  devoid  of  any  masticatory  or  diges- 


FIG.  43. — Botifera.  A.  Diagrammatic  representation  of  Uydatina  senta  (generalized  from 
Pritchard) :  a  Depression  in  the  ciliated  disk  leading  to  the  digestive  canal ;  &  Mouth ; 
c  Pharyngeal  bulb  with  masticatory  apparatus ;  d  Stomach ;  e  Cloaca ;  /  Contractile 
bladder ;  g  ff  Eespiratory  or  water-vascular  tubes ;  Ji  Nerve-ganglion,  giving  filament  to 
ciliated  pit  (£) ;  o  Ovary.  B.  Melicerta  ringens  (after  Gosse). 

tive  apparatus,  and  more  or  less  closely  resembling  the  young 
forms  of  the  species.  The  males,  in  fact,  merely  lead  a  tran- 
sient existence,  and  die  as  soon  as  they  have  succeeded  in 
fertilizing  the  females.  The  body  in  most  cases  is  very  dis- 
tinctly ringed  or  annulated  (Fig.  43,  A),  but  is  not  composed 
of  distinct  rings  separated  by  partitions.  The  integument  is 
usually  provided  with  bundles  of  muscular  fibres  taking  a 
longitudinal  and  transverse  direction.  In  the  free  forms  the 


SCOLECIDA.  117 

anterior  ciliated  disk  acts  somewhat  like  the  propeller  of  a 
screw-steamer  in  driving  the  organism  through  the  water — in 
all  cases  it  has  the  action  of  producing  currents  in  the  water 
by  which  particles  of  food  are  brought  to  the  mouth.  The 
posterior  end  of  the  body  is  usually  developed  in  the  free 
forms  into  a  kind  of  tail  or  foot  (Fig.  43,  A),  which  may  take 
the  shape  of  a  kind  of  pincers  or  of  a  little  suctorial  disk. 

As  regards  their  internal  anatomy,  in  the  females  of  almost 
all  the  Rotifera  there  is  a  well-developed  alimentary  canal, 
which  is  completely  shut  off  from  the  general  cavity  of  the 
body.  The  mouth  (Fig.  43,  A  b)  opens  into  a  dilated  cham- 
ber (c),  which  contains  a  complicated  apparatus  of  horny 
teeth.  This  in  turn  opens  into  a  capacious  stomach  (c?),  con- 
tinued into  an  intestine  which  terminates  by  a  chamber  known 
as  the  "cloaca"  (e),  which  forms  the  common  outlet  for  the 
water-vascular  and  generative  systems.  In  both  sexes  there 
is  a  well-developed  water-vascular  system  consisting  of  a  con- 
tractile chamber  or  bladder  (/"),  opening  into  the  cloaca,  and 
giving  origin  to  two  complicated  tubes  which  are  known  as 
the  "respiratory  tubes"  (g  </),  and  which  terminate  near  the 
anterior  end  of  the  body,  apparently  by  blind  extremities. 
The  nervous  system  is  in  the  form  of  a  large  double  ganglion 
placed  above  the  gullet,  and  having  one  or  two  eye-specks 
placed  upon  it.  The  ovaries  (o)  constitute  conspicuous  organs 
in  the  female  Rotifera,  but  in  summer  the  young  Rotifers  ap- 
pear to  be  produced  by  the  females  without  having  access  to 
the  males. 

The  Rotifera  were  long  confounded  with  the  Infusoria,  in 
consequence  of  their  great  similarity  in  external  appearance. 
They  are,  however,  of  an  obviously  much  higher  grade  of 
structure.  One  of  the  most  remarkable  phenomena  presented 
by  the  Rotifera  is  found  in  the  undoubted  fact  that,  in  spite 
of  their  complex  organization  and  aquatic  habits,  they  can  be 
dried,  and  again  brought  to  life  by  the  addition  of  a  little 
water,  and  that  this  desiccation  and  restoration  to  life  can  be 
apparently  repeated  many  times  in  succession  without  injury. 


SUB-KINGDOM  IV.—ANNULOSA. 
CHAPTER  XII. 

AN  ARTHROPOD  A. 

SUB-KINGDOM  ANNULOSA. — In  this  sub-kingdom  are  com- 
prised an  enormous  number  of  animals  which  agree  in  the 
following  characters  (Fig.  44)  :  The  body  is  composed  of  a 
number  of  segments  or  rings  arranged  along  a  longitudinal 
axis.  There  is  a  distinct  alimentary  canal  (#),  placed  cen- 
trally as  compared  with  the  other  organic  systems,  and  com- 
pletely shut  off  from  the  general  cavity  of  the  body.  The 


FIG.  44.— Diagram  of  an  Aunulose  animal,    a  Blood- vascular  or  hsomal  system;  &  Digestive 
system ;  c  Neural  system. 

blood-vascular  system  may  be  absent,  but,  when  present,  it  is 
always  situated  on  the  dorsal  aspect  of  the  body  (a).  The 
nervous  system  is  always  present,  and  is  placed  along  the 
ventral  surface  of  the  body.  In  its  typical  form  it  consists 
of  two  nervous  cords  running  along  the  whole  length  of  the 
ventral  surface,  and  having  a  pair  of  ganglia  developed  in 
each  ring.  The  first  pair  of  ganglia  is  always  placed  above 
the  gullet,  and  the  second  below,  so  that  the  gullet  is  sur- 
rounded by  the  two  cords  uniting  these  ganglia  (constituting 
the  so-called  cesophageal  collar).  The  limbs  (when  present) 
are  always  turned  toward  the  neural  aspect — that  is  to  say,, 


ANARTHROPODA.  119 

toward  that  side  of  the  body  upon  which  the  nervous  system 
is  situated.  (See  also  the  transverse  section  of  an  Annulose 
animal,  Fig.  1.)  The  entire  sub-kingdom  of  the  Annulosa  is 
divided  into  two  great  divisions  termed  Arthropoda  and 
Anarthropoda,  according  as  the  body  is  provided  with  jointed 
appendages  or  not.  In  the  Arthropoda.  in  which  the  body- 
rings  are  furnished  (some  or  all)  with  jointed  appendages,  are 
included  the  Crustaceans  (lobsters,  crabs,  etc.),  the  spiders  and 
scorpions,  the  centipedes,  and  the  insects.  In  the  Anarthro- 
poda,  in  which  there  are  no  true  jointed  appendages,  are  in- 
cluded the  spoon-worms,  leeches,  earth-worms,  tube-worms, 
and  sand- worms.* 

DIVISION  I.  ANARTHROPODA  (Gr.  a,  without ;  arthros,  joint ; 
podes,  feet). — In  this  division  of  the  Annulosa,  the  locomotive 
appendages  are  never  distinctly  jointed  or  articulated  to  the 
body.  In  this  division  are  included  two  principal  classes — the 
Gephyrea  and  the  Annelida.\ 

CLASS  I.  GEPHYREA. — This  class  is  a  very  small  one,  and 
includes  a  number  of  worm-like  animals,  which  in  most  re- 
spects are  very  similar  to  the  following  class  of  the  Annelida, 
but  are  distinguished  by  having  no  locomotive  appendages  at- 
tached to  the  sides  of  the  body.  They  were  long  placed  among 


FIQ.  45. — Gephyrea.    Syrinx  nudus  (after  Forbes). 

the  Echinodermata,  having  a  decided  relationship  to  the  worm- 
like  Holothurians.  They  are  distinguished,  however,  by  never 
secreting  calcareous  matter  in  the  skin,  and  by  having  no 
water-vascular  or  ambulacral  system.  There  can  be  no  doubt, 

*  The  Anarthropoda  are  often  united  with  the  Scolecida  into  a  common  sub-kingdom 
under  the  name  of  Vermes;  in  which  case  the  EcMnodermata  are  retained  apart  in  a 
special  sub-kingdom. 

t  A  third  class  has  been  constituted  under  the  name  of  CTicetognatha  for  some  singular 
marine  animals,  transparent  and  worm-like  in  form,  with  lateral  fins  at  the  hinder  end  of  the 
body,  and  having  the  mouth  armed  with  bristles.  They  form  the  genus  Sagitta. 


120  INVERTEBRATE  ANIMALS. 

however,  that  the  Gephyrea  are,  on  the  whole,  very  nearly 
related  to  the  Holothurians,  and  it  is  chiefly  from  the  total 
absence  of  any  radiate  arrangement  of  the  nervous  system  and 
internal  organs  that  they  appear  to  be  more  properly  classed 
with  the  worms.  The  Sipunculus  or  spoon-worm  is  found 
burrowing  in  the  sand  of  many  sea-coasts,  or  inhabiting  the 
cast-away  shells  of  univalve  shell-fish.  A  considerable  num- 
ber of  species  of  this  class  have  been  recorded  as  occurring  in 
European  seas,  and  one  of  the  more  characteristic  forms  is 
figured  above  (Fig.  45). 

CLASS  II.  ANNELIDA  (Lat.  annulus,  a  ring). — The  Annelida 
or  ringed-worms  are  distinguished  from  the  preceding  by  the 
possession  of  definite  segmentation,  the  body  being  composed 
of  a  number  of  rings  which  are  all  similar  to  each  other  ex- 
cept at  the  two  ends  of  the  body.  All  the  Annelida  are  more 
or  less  worm-like  in  shape,  and  in  all,  except  the  leeches,  the 
segments  are  (some  or  all)  provided  with  lateral  appendages 
which  mostly  subserve  locomotion,  but  which  are  never  jointed 
to  the  body.  In  the  typical  Annelida  each  segment  (Fig.  46) 


FIG.  46. — Diagrammatic  transverse  section  of  a  typical  Annelide.  d  Dorsal  arc ;  v  Ventral 
arc;  n  Branchiae  or  gills;  a  Dorsal  oar;  &  Ventral  oar— both  carrying  bristles  and  a 
jointed  filament 

consists  of  two  arches,  termed,  from  their  position,  respectively 
the  "dorsal  arc"  (d),  and  the  "ventral  arc"  (v).  Each  seg- 
ment carries  a  lateral  process  on  each  side,  which  are  known 
as  the  "foot-tubercles"  (parapodia).  Each  foot-tubercle  in 
turn  may  consist  of  an  upper  piece  or  "  dorsal  oar  "  (a),  and  a 
lower  piece  or  "  ventral  oar  "  (£),  both  carrying  a  tuft  of  bris- 
tles and  a  soft  jointed  filament. 

The  nervous  system  consists  essentially  of  a  double  gan- 
gliated  chain  placed  along  the  ventral  surface  of  the  body,  and 


ANARTHROPODA.  121 

traversed  in  front  by  the  gullet,  so  that  the  first  ganglion  lies 
above  the  gullet  (Fig.  44).  The  digestive  system  consists  of 
a  mouth,  generally  with  a  protrusible  proboscis,  and  sometimes 
horny  jaws,  a  gullet,  stomach,  intestine,  and  a  distinct  anus. 
As  a  rule,  the  alimentary  canal  runs  straight  from  one  end  of 
the  body  to  the  other  without  describing  any  convolutions  in 
its  course.  In  almost  all  cases  the  alimentary  tube  is  placed 
in  a  distinct  cavity,  which  contains  a  fluid  with  solid  par- 
ticles in  it,  believed  to  correspond  to  the  blood  of  the  higher 
Annulosa.  In  most,  if  not  in  all,  there  is  an  additional  system 
of  vessels  which  carry  a  fluid  containing  solid  particles,  which 
are  contractile,  and  which  send  branches  to  the  respiratory 
organs,  when  these  exist.  This  system  is  believed  not  to  cor- 
respond to  the  blood-vascular  system  of  the  higher  animals, 
and  it  has,  therefore,  been  termed  the  "  pseudo-haemal "  system 
(Gr.  pseudos,  falsity ;  and  haima,  blood).  It  is  believed,  on 
the  other  hand,  to  be  truly  homologous  with  the  water-vascu- 
lar system  of  the  Annuloida.  Respiration  is  effected  by  the 
general  surface  of  the  body,  or  by  distinct  gills  or  branchiae. 
In  most  cases,  also,  there  exists  a  series  of  peculiar  involutions 
of  the  integument,  which  are  known  as  the  "  segmental  or- 
gans "  or  "  respiratory  pouches,"  and  which  are  believed  to 
be  partially  concerned  in  the  respiratory  process.  The  sexes 
in  the  Annelida  are  sometimes  distinct,  sometimes  united  in 
the  same  individual.  The  embryos  are  almost  always  ciliated, 
and  many  of  them  pass  through  a  metamorphosis. 
The  Annelida  may  be  divided  as  follows : 

SECTION  A.  ABRANCHIATA. — Without  gills  or  branchiae. 

1.  Hirudinea. — (Leeches.) 

2.  Oligochceta. — (Earth-worms.) 
SECTION  B.  BRANCHIATA. — With  branchiae. 

3.  Tubicola. — Tube- worms.) 

4.  Errantia. — (Sand-worms.) 

ORDER  I.  HIRUDINEA  (Lat.  hirudo,  a  horse-leech). — This 
order  comprises  only  the  leeches,  some  of  which  are  marine, 
while  others  inhabit  fresh  water.  The  leeches  (Fig.  47)  are 
all  characterized  by  the  fact  that  the  body  is  destitute  of 
lateral  bristles  or  foot-tubercles,  but  is  provided  with  a  suck- 
ing-disk at  one  or  both  extremities.  In  the  typical  forms,  as 
in  the  common  medicinal  leech,  there  are  sucking-disks  at 
both  ends  of  the  body,  and  in  those  in  which  only  the  hinder 
sucker  is  present,  the  head  can  be  converted  into  a  suctorial 


122 


INVERTEBRATE  ANIMALS. 


cavity.  Locomotion  is  effected  either  by  means  of  the  alter- 
nate fixation  and  detachment  of  the  suckers,  or  by  a  serpentine 
bending  of  the  body. 

The  body  is  obviously  ringed  or  annulated,  but  none  of 
the  rings  carry  lateral  appendages  of  any  kind.  The  mouth 
is  sometimes  destitute  of  teeth,  but  is  occasionally  armed  with 
complex  jaws.  The  alimentary  canal 
is  short,  with  lateral  dilatations,  and 
united  to  the  skin  by  means  of  a 
spongy  vascular  tissue,  so  that  the  body- 
cavity  is  obliterated.  The  pseudo- 
hsemal  system  is  well  developed,  and 
consists  essentially  of  four  great  longi- 
tudinal vessels.  Respiration  appears 
to  be  effected,  in  part,  at  any  rate, 
by  means  of  the  segmental  organs, 
which  have  the  form  of  little  sacs 
opening  externally  by  minute  aper- 
tures. The  nervous  system  has  its 
usual  form,  and  the  ganglia  in  front  of 
the  gullet  (" prce-atsophageaV  ganglia) 
give  off  branches  to  a  number  of  simple 
eyes  which  are  placed  on  the  head. 
The  sexes  are  united  in  the  same  in- 
dividual. 

The  most  familiar  of  the  leeches  are 
the  common  horse-leech   (Hcemopsis), 
medicinal  leech  (Sanguisuga 
s,  Fig.  47).     The  former  has 
small  and  blunt  teeth,  but  the  latter  is 
provided  with  three  semicircular  tooth- 
ed jaws  (Fig.  47,  #,  c),  which  meet  in  a 

point,  and  are  sufficiently  powerful  to  cut  through  the  human 
skin.  The  medicinal  leech  is  a  native  of  fresh  waters  through- 
out the  south  and  east  of  Europe,  and  it  is  imported  in  large 
numbers  from  Hungary,  Bohemia,  and  Russia. 

ORDER  II.  OLIGOCH^ETA. — In  this  order  are  included  the 
earth-worms  (iMmbricidce),  and  the  water- worms  (N~dididce). 
They  are  all  distinguished  from  the  preceding  by  the  fact 
that  the  body  is  furnished  with  rows  of  bristles  which  take 
the  place  of  the  foot-tubercles  of  the  higher  Annelida,  and 
which  are  the  organs  of  locomotion.  They  are  distinguished 
from  the  higher  forms  by  the  fact  that  the  locomotive  bristles 


FIG.  47.—  Hirudinea.  a  The  me- 


sucker  and  triradiate  }aws; 


toothed  margin. 


ANARTHROPODA. 


123 


are  comparatively  few  in  number,  hence  the  modern  name  of 
the  order  (Gr.  oligos,  few ;  and  chaite,  a  bristle).  In  the  com- 
mon earth-worm  (Lumbricus  terrestris)  the  body  is  cylindrical, 
attenuated  at  both  ends,  and  furnished  with  eight  rows  of 
locomotive  bristles.  The  mouth  is  destitute  of  teeth,  and 
opens  into  a  gullet  which  leads  to  a  muscular  crop,  succeeded 
by  a  second  muscular  dilatation  or  gizzard.  The  intestine  is 
continued  straight  to  the  anus,  and  is  constricted  in  its  course 
by  numerous  transverse  partitions  springing  from  the  walls 
of  the  body-cavity.  The  pseudo-haemal  system  is  well  de- 
veloped ;  and  there  exists  in  even  greater  numbers  than  in 
the  leeches  the  series  of  segmental  organs,  or  lateral  pouches, 
which  open  externally  by  pores.  The  JtfdididoB  are  chiefly 
noticeable  on  account  of  their  power  of  producing  fresh  indi- 
viduals by  a  process  of  budding  before  they  attain  sexual 
maturity.  One  of  the  commonest  of  them  is  a  little  worm 
which  occurs  abundantly  in  many  pools  and  streams  (Tubifex 
rivulorum),  and  which  exhibits  a  fine  red  color,  owing  to  the 
pseudo-haemal  system  being  visible  through  the  transparent 
integument. 

OKDEE  III.  TUBICOLA. — The  Annelides  included  in  this 
group  derive  their  name  from  the 
fact  that  they  have  the  power  of 
protecting  themselves  by  means  of 
tubes  (Lat.  tuba,  a  tube;  and  colot 
I  inhabit).  In  some  cases  (Fig. 
48)  the  tube  is  composed  of  car- 
bonate of  lime,  and  is  a  genuine 
secretion  from  the  body.  In  all 
the  Tubicola  the  respiratory  organs 
are  in  the  form  of  branched  fila- 
mentous external  gills,  in  which 
the  fluid  of  the  pseudo-haemal  sys- 
tem is  subjected  to  the  action  of 
the  outer  water.  They  are,  there- 
fore, "  branchiate  "  Annelides.  As  FIG.  48.— TWcoia, 
they  live  in  tubes,  however,  and 
do  not  voluntarily  expose  more 
than  the  anterior  end  of  the  body, 
the  branchiae  are  all  placed  on  or  near  the  head.  The  filaments 
of  which  the  gills  are  composed  (Fig.  48,  a)  are  richly  ciliated, 
and,  as  the  pseudo-haemal  fluid  is  usually  red,  they  have  gen- 
erally a  beautiful  scarlet  color. 


a  Serpuia  con- 


124 


INVERTEBRATE   ANIMALS. 


The  most  familiar  of  the  Tubicola  is  the  Serpula  (Fig. 
48,  #),  the  contorted  and  winding  tubes  of  which  must  be 
known  to  every  one  as  occurring  on  shells  or  stones  on  the 
sea-shore.  One  of  the  cephalic  filaments  in  Serpula  is  much 
developed,  and  its  extremity  forms  a  kind  of  conical  plug 
which  serves  to  close  the  mouth  of  the  tube  when  the  animal 
is  retracted  within  it.  In  Spirorbis  (Fig.  48,  b)  the  shelly  tube 
is  coiled  into  a  flat  spiral,  which  is  fixed  to  some  solid  object. 
It  is  of  extremely  common  occurrence  on  the  fronds  of  sea- 
weed, and  on  other  submarine  objects. 

ORDER  IV.  ERRANTIA. — The  Annelides  comprised  in  this 
order  are  called  "  errant "  (Lat.  erro,  I  wander),  or  "  roving," 
from  the  fact  that  they  all  lead  a  free  existence,  and  are  never 
confined  in  tubes.  They  have  always  lateral  unjointed  ap- 
pendages, or  foot-tubercles  (Fig.  49),  which  carry  tufts  of 


FIG.  49.— Errant  Annelides.    A.  Hairy  Bait  (yepJithys);  B.  Sea-Mouse  (Aphrodite) ;  C. 
Lobworm  (Arenicola).    (After  Gosse.) 

bristles  and  a  soft,  jointed  filament.  The  anterior  rings  of 
the  body  are  usually  so  modified  as  to  form  a  sort  of  head, 
which  is  provided  with  eyes  and  with  two  or  more  feelers, 
which  differ  from  the  antennas  of  insects  and  Crustaceans  in 
not  being  jointed.  The  mouth  is  placed  on  the  inferior  sur- 
face of  the  head,  and  is  sometimes  furnished  with  one  or  more 
pairs  of  horny  jaws,  which  work  from  side  to  side.  The  upper 


ANARTHROPODA.  125 

part  of  the  alimentary  canal  is  muscular,  and  can  be  turned 
inside  out,  or  protruded  beyond  the  true  opening  of  the 
mouth.  The  pseudo-hsetnal  system  is  well  developed,  and  its 
contained  fluid  is  mostly  red.  Respiration  is  effected  by  ex- 
ternal processes,  gills,  or  branchiae,  arranged  in  tufts  placed 
along  the  sides  or  back  of  the  body,  and  not  confined  to  the 
immediate  neighborhood  of  the  head,  as  in  the  Tubicola.  The 
sexes  are  in  different  individuals,  and  the  young  pass  through 
a  metamorphosis. 

Among  the  best  known  and  commonest  of  the  Errant  Anne- 
lides  are  the  common  lob-worm  (Arenicola  piscatorum)  of  our 
coasts,  which  is  constantly  used  by  fishermen  for  bait ;  and  the 
sea-mice  (Aphrodite  and  Polynoe\  some  of  which  attain  a  large 
size,  and  are  conspicuous  for  their  iridescent  bristles.  Other 
less  abundant  forms  may  be  readily  obtained  by  searching 
under  stones  at  low  water. 


CHAPTER  XIII. 
AETHEOPODA. 

DIVISION  II.  AETHEOPODA  or  AETICULATA. — The  members 
of  the  sub-kingdom  Annulosa  comprised  under  this  head  are 
generally  known  as  Articulate  animals,  or  as  Arthropoda  (Gr. 
arthros,  a  joint ;  and  podes,  feet).  They  are  all  distinguished 
by  the  possession  of  jointed  appendages  articulated  to  the  body. 
The  body  is  composed  of  a  series  of  distinct  rings  or  segments 
(technically  called  "  somites  ")  arranged  longitudinally  one  be- 
hind the  other.  The  skin  is  more  or  less  completely  hardened 
by  a  horny  deposit  of  "  chitine,"  with  or  without  lime,  so  as  to 
form  a  resisting  shell,  to  the  inner  surface  of  which  the  muscles 
are  attached.  There  is  consequently  no  necessity  for  any  in- 
ternal skeleton.  The  nervous  S3rstem  in  the  young  of  all 
Articulate  animals  has  its  typical  form  of  a  chain  of  ganglia 
placed  along  the  ventral  surface  of  the  body,  and  traversed  in 
front  by  the  gullet.  In  the  adult,  however,  this  typical  state 
of  the  nervous  system  is  often  lost  or  modified.  The  blood- 
circulatory  system  may  be  absent ;  but,  when  it  is  present,  it  is 
placed  dorsally  (Fig.  44),  and  consists  of  a  true  blood-system 
containing  corpusculated  blood,  and  furnished  with  a  contractile 
cavity  or  heart.  Respiration  is  sometimes  effected  simply  by 
the  general  surface  of  the  body,  but  there  are  generally  special 
organs  adapted  for  breathing  air,  either  directly  or  through  the 
medium  of  water.  Jointed  appendages  are  always  present,  and 
may  be  developed  from  any  segment  of  the  body. 

The  Arthropoda  are  divided  into  four  great  classes — viz., 
the  Crustacea  (crabs,  lobsters,  etc.),  the  Arachnida  (mites, 
spiders,  and  scorpions),  the  Myriapoda  (centipedes  and  gally- 
worms),  and  the  Insecta  (or  true  insects).  These  are  roughly 
distinguishable  from  one  another  by  the  following  charac- 
ters 


ARTHROPOD  A.  127 

1.  CRUSTACEA. — Animal  more  or  less  truly  aquatic ;  respiration  by  gills, 
or  by  the  general  surface  of  the  body ;  two  pairs  of  antennae  (feelers) ;  loco- 
motive appendages  more  than  eight  in  number,  borne  by  the  segments  of  the 
thorax,  and  usually  of  the  abdomen  also. 

2.  ARACHNIDA. — Respiration    aerial,   by  pulmonary  sacs,   by  air-tubes 
(tracheae),  or  by  the  general  surface  of  the  body ;  head  and  thorax  amalga- 
mated ;  antennae  ( as  such),  absent ;   legs  eight ;  abdomen  without  jointed 
appendages. 

3.  MYRIAPODA. — Respiration  by  air-tubes  (tracheae)  ;  head  distinct ;  re- 
mainder of  the  body  composed  of  nearly  similar  segments ;   one  pair  of 
antennae ;  legs  numerous. 

4.  INSECTA. — Respiration    by   air-tubes   (tracheae) ;    head,   thorax,   and 
abdomen  distinct ;  one  pair  of  antennae ;  three  pairs  of  legs  borne  on  the 
thorax ;  abdomen  destitute  of  limbs  ;  generally  two  pairs  of  wings  on  the 
thorax. 


CHAPTER    XIV. 
CRUSTACEA. 

CLASS  I.  CKTTSTACEA  (Lat.  crusta,  a  crust,  or  external 
shell). — The  members  of  this  class  are  commonly  known  as 
crabs,  lobsters,  shrimps,  prawns,  king-crabs,  barnacles,  acorn- 
shells,  wood-lice,  etc.  They  are  nearly  allied  to  the  succeeding 
class  of  the  Arachnida  (spiders  and  scorpions),  but  are  dis- 
tinguished by  their  adaptation  to  a  more  or  less  purely  aquatic 
life,  by  having  jointed  appendages  upon  the  hinder  segments 
of  the  body  (abdomen),  and  by  the  possession  of  two  pairs  of 
antennae.  As  a  class,  the  Crustacea  are  distinguished  by 
being  usually  furnished  with  branchiae  or  respiratory  organs 
adapted  for  breathing  air  dissolved  in  water,  by  having  more 
than  four  pairs  of  legs,  by  having  a  well-developed  chitinous 
or  partially  calcareous  "crust"  or  external  skeleton,  by  the 
fact  that  some  of  the  appendages  are  generally  so  modified  as 
to  act  as  organs  of  mastication,  and  by  passing  through  a  meta- 
morphosis before  attaining  their  adult  condition. 

The  body  in  a  typical  Crustacean  is  composed  of  twenty-one 
(or,  according  to  some  writers,  twenty)  distinct  segments  or 
somites,  placed  one  behind  the  other.  These  segments  are 
distributed  in  three  distinct  divisions,  known  respectively  as 
the  "  head,"  the  "  thorax  "  or  chest,  and  the  "  abdomen  "  or 
tail,  each  of  which  is  usually  regarded  as  being  composed  of 
seven  segments.  In  very  many  cases,  however,  the  fourteen 
segments  belonging  to  the  head  and  chest  are  amalgamated 
together  into  a  single  mass,  which  is  termed  the  "  cephalo- 
thorax,"  thus  leaving  seven  segments  to  the  abdomen.  It 
will  be  unnecessary,  however,  to  dwell  here  longer  upon  the 
structure  of  the  Crustacea,  as  the  general  morphology  of 
the  class  will  be  given  at  somewhat  greater  length  in  speak- 
ing of  the  lobster.  The  classification,  also,  of  the  Crustacea 


CRUSTACEA.  129 

is  so  complex  that  it  will  be  as  well  to  omit  altogether  the 
less  important  orders,  merely  giving  the  names  and  leading 
characters  of  these  in  an  appendix.  It  has  also  been  thought 
advisable  to  invert  the  usual  order  here  adopted,  and  to  com- 
mence with  the  consideration  of  the  highest  sections  of  the 
class  first. 

OKDER  DECAPODA. — The  Crustacea  included  in  this  order 
derive  their  name  from  the  fact  that  they  all  possess  five  pairs 
of  legs  (Gr.  deka^  ten ;  podes,  feet).  They  belong  to  a  large 
section  known  as  the  "  stalk-eyed  "  Crustaceans,  from  the  fact 
that  the  eyes  are  supported  by  long,  movable  stalks.  They 
include  the  lobsters,  shrimps,  cray-fish,  crabs,  hermit-crabs,  and 
other  forms,  and  are  the  most  highly  organized  and  most  familiar 
of  the  whole  class  of  the  Crustacea.  They  are  divided  into 
three  very  well  marked  groups  or  tribes,  all  of  which  can  be 
exemplified  by  the  well-known  British  species. 

A.  Macrura. — The  name  of  Macrura  (Gr.  makros,  long; 
and  owra,  tail)  is  given  to  those  ten-footed  Crustaceans  which 
have  a  long  and  well-developed  tail.  Among  these  are  the 
lobster,  shrimp,  prawn,  and  cray-fish,  of  which  the  lobster  may 
be  selected  as  a  good  typical  example. 

In  the  lobster  (Fig.  50)  the  body  is  at  once  seen  to  be 
composed  of  two  parts,  familiarly  called  the  "head"  and 
"  tail."  The  so-called  head  is  covered  by  a  great  shield  termed 
the  "carapace"  (Fig.  50,  ca),  and  it  is  in  reality  the  cephalo- 
thorax,  being  composed  of  the  amalgamated  segments  which 
belong  to  the  true  head  and  to  the  thorax.  The  so-called 
tail  is  really  the  abdomen,  and  it  is  composed  of  a  number  of 
segments  which  are  not  immovably  united  together,  as  in  the 
cephalo-thorax,  but  are  movably  jointed  together.  The  vari- 
ous appendages  of  the*  animal  are  arranged  in  pairs  on  the 
under  surface  of  the  body ;  and,  where  the  segments  are  com- 
pletely amalgamated  (as  in  the  cephalo-thorax),  their  existence 
may,  nevertheless,  be  determined  by  the  presence  of  a  pair  of 
appendages.  The  first  segment  of  the  head  carries  a  pair  of 
compound  eyes,  made  up  of  a  number  of  simple  lenses  aggre- 
gated together,  and  supported  upon  long  and  movable  eye- 
stalks.  Behind  these  come  two  pairs  of  jointed  organs  of 
touch,  which  are  known  as  the  "  antennas."  The  front  pair  is 
much  smaller  than  the  hinder  pair,  and  they  are  known  re- 
spectively as  the  "lesser  antennas,"  or  " antennules,"  and 
the  "  great  antennas."  Behind  these,  again,  comes  the  mouth, 
which  is  placed  on  the  under  surface  of  the  head,  and  is  pro- 


130 


INVERTEBRATE  ANIMALS. 


vided  with  a  complicated  series  of  masticatory  organs.  It  is 
unnecessary  to  describe  these  minutely,  but  it  should  be 
noticed  that  they  are  all  modified  limbs,  and  therefore  differ 


FIG.  50.— Common  Lobster  (Hbmarus  vulgaris).  1.  First  pair  of  legs,  constituting  the 
great  nipping-claws ;  2  and  3.  Second  and  third  pairs  of  legs,  also  ending  in  nipping- 
claws  ;  4  and  5.  Last  two  pairs  of  legs ;  a  Smaller  antennae ;  ga  Greater  antennae ;  ca 
Carapace. 

altogether  from  the  jaws  of  the  Vertebrate  animals.  That 
this  is  their  real  nature  is  shown  most  obviously  in  the  hind- 
most pairs  of  these  jaws,  which  are  so  little  altered  from  ordi- 
nary legs  that  they  are  known  as  "  foot-jaws."  The  last  five 


CRUSTACEA.  131 

segments  of  the  thorax  carry  five  pairs  of  walking-legs,  hence 
the  name  Decapoda  applied  to  the  order.  Of  these  legs,  the 
first  three  pairs  have  their  extremities  converted  into  nipping- 
claws  or  "  chelge,"  and  the  first  pair  is  much  larger  than  the 
others,  and  constitutes  the  well-known  great  claws  of  the  lob- 
ster. The  last  two  pairs  of  legs  simply  terminate  in  pointed 
extremities,  and  not  in  pincers.  The  segments  of  the  abdo- 
men, with  the  exception  of  the  hindmost,  carry  each  a  pair  of 
paddle-like  appendages,  which  are  used  in  swimming,  and  are 
called  the  "swimmerets."  The  last  pair  of  swimmerets  are 
attached  to  the  last  segment  but  one,  and  are  very  greatly  ex- 
panded, so  as  to  form  a  very  powerful  tail-fin.  The  last  seg- 
ment of  all  is  known  as  the  "  telson,"  and  is  not  provided  with 
any  lateral  appendages. 

"  The  mouth  in  the  lobster  leads  by  a  short  gullet  into  a 
globular  stomach,  which  is  furnished  with  a  calcareous  appa- 
ratus for  grinding  down  the  food,  commonly  called  the  "  lady 
in  the  lobster."  The  intestine  is  continued  backward  from 
the  stomach  without  convolutions,  and  opens  by  a  distinct 
anus  placed  in  front  of  the  telson.  A  well-developed  liver  is 
also  present.  The  heart  is  placed  dorsally,  and  is  filled  with 
aerated  blood  derived  from  the  gills,  which  it  propels  through 
every  part  of  the  body.  The  gills,  or  branchiae,  are  pyrami- 
dal bodies  attached  to  the  bases  of  the  legs,  and  placed  in 
a  kind  of  chamber  formed  beneath  the  great  shield,  or  cara- 
pace, on  each  side  of  the  body.  They  consist  each  of  a  central 
stem  supporting  numerous  lateral  branches,  and  they  are  richly 
supplied  with  blood.  The  water  which  fills  the  gill-chambers 
is  constantly  renewed  by  the  movements  of  the  legs,  and  thus 
the  gills  are  kept  constantly  supplied  with  fresh  water.  The 
nervous  system  is  placed  along  the  ventral  surface  of  the  body, 
and  has  its  usual  form.  The  organs  of  sense 'are  the  two  pairs 
of  feelers  or  antennae,  the  compound  eyes,  and  two  organs  of 
hearing. 

B.  Anomura. — The  most  familiar  members  of  this  tribe 
are  the  hermit-crabs  (Paguridce)  which  occur  so  commonly  on 
every  shore.  They  are  distinguished  by  the  fact  that  the  ab- 
domen is  quite  soft,  and  is  not  protected  by  a  chitinous  crust. 
The  animal,  therefore,  is  compelled  to  protect  the  defenceless 

Eart  of  the  body  in  some  artificial  manner,  and  this  it  effects 
y  appropriating  the  empty  shell  of  some  dead  mollusk,  such 
as  the  common  periwinkle  or  whelk.     The  abdomen  is  pro- 
vided with  special  appendages  to  enable  the  intruder  to  re- 
tain firm  hold  of  his  borrowed  dwelling,  at  the  same  time  that 


132  INVERTEBRATE  ANIMALS. 

he  can  change  it  at  will  when  too  small  or  otherwise  incon- 
venient. The  first  pair  of  legs  are  developed  into  pretty 
powerful  nipping-claws  or  chelee,  and  one  of  them  is  always 
much  larger  than  the  other,  and  acts  as  a  kind  of  plug,  block- 
ing up  the  entrance  of  the  shell  when  the  animal  is  retracted 
within  it. 

C.  Brachyura. — The  decapod  Crustaceans  included  in 
this  tribe  are  familiarly  known  as  crabs,  and  they  derive  their 
name  of  Brachyura  (G.  brachus,  short ;  and  oura,  tail)  from 


FIG.  51. — Brachyura.    The  Spiny  Spider-crab  (Mala  squinado), 

the  rudimentary  condition  of  the  abdomen.  The  abdomen,  in 
fact,  is  not  only  extremely  short,  but  it  is  always  tucked  up 
beneath  the  greatly-developed  cephalo-thorax,  so  that  it  is  not 
visible  at  all,  except  when  the  animal  is  looked  at  from  below 
(Fig.  51).  The  crabs  are  very  various  in  their  habits,  but  they 
are  mostly  denizens  of  the  shore,  hiding  beneath  stones  or  sea- 


CRUSTACEA. 


133 


weed,  in  cracks  of  rock,  or  in  pools  near  the  line  of  low  water. 
Some  of  them,  however,  can  swim  with  tolerable  activity,  and 
some  of  them  (the  land-crabs)  even  live  habitually  inland. 
One  group,  the  "  pea-crabs,"  is  distinguished  by  the  singular 
habit  of  living  semi-parasitically  within  the  shells  of  bivalve 
mollusks,  such  as  the  great  horse-mussel. 

The  young  or  larval  crab  is  exceedingly  unlike  the  adult, 
and  has  a  long  and  well-developed  abdomen,  thus  approximat- 
ing to  the  type  of  structure  which  is  permanently  retained  in 
the  Macrura. 


ORDER  ISOPODA  (Gr.  isos,  equal;  podes,  feet).— In  this 
order  are  a  number  of  Crus- 
taceans of  which  some  in- 
habit the  sea,  others  are 
parasitic  in  their  habits,  and 
others  are  terrestrial.  The 
best  known  are  the  common 
wood-lice  (Oniscus^  Fig.  52), 
which  are  found  so  com- 
monly under  stones,  or  in 
the  crevices  of  old  walls. 
The  Isopods  all  belong  to 
a  group  of  Crustaceans  in 
which  the  eyes  are  not  sup- 
ported upon  stalks,  and  they 
are  therefore  said  to  be  "ses- 
sile-eyed." The  head  is  dis- 
tinct from  the  segment  bear- 
ing the  first  pair  of  feet.  The 
thoracic  feet  are  all  similar 
to  one  another,  and  the  bran- 
chiae are  developed  on  the 
abdominal  legs. 


FIG.  52.— Isopoda.    Wood-lice  (Oniscus). 


ORDER  MEROSTOMATA. — In  this  order  are  only  the  living 
king-crabs  (Limulus),  and  some  large  extinct  forms  nearly 
allied  to  them.  They  are  all  distinguished  by  the  fact  that 
the  appendages  which  are  placed  round  the  mouth  act  by 
their  bases  as  jaws,  but  have  their  extremities  developed  into 
swimming-paddles,  walking-feet,  or  nipping-claws. 

The  King-crabs  or  Horseshoe  crabs  (Fig.  53)  constitute  a 
special  group  called  Xiphosura  (Gr.  xiphos,  a  sword ;  and 
7 


134 


INVERTEBRATE  ANIMALS. 


our  a,  tail),  from  the  fact  that  the  end  of  the  abdomen  is 
furnished  with  a  long  sword-like  spine  (Fig.  53,  tf).  The 
mouth  is  surrounded  by  six  pairs  of  appendages,  the  bases  of 
which  are  spinous  and  act  as  jaws,  while  their  free  extremities 
are  developed  into  nipping-claws  or  chelae.  The  whole  of  the 
upper  surface  of  the  body  is  protected  by  a  kind  of  buckler, 
composed  of  an  anterior  semicircular  shield,  and  a  posterior 
'somewhat  hexagonal  plate,  the  under  surface  of  which  carries 


FIG.  53.  — Xiphosura.    Limulus  poly- 
phemus,  viewed  from  below. 


FIG.  54.  — Eurypterida.  Pterygotua 
Anglicw,  restored  (after  H.  Wood- 
ward). 


branchial  plates,  while  the  sword-like  telson  is  jointed  to  its 
hinder  margin.  The  king-crabs  attain  a  large  size,  and  are 
often  called  "  Molucca  crabs "  from  their  occurrence  in  the 
Moluccas.  Both  the  eggs  and  the  flesh  are  eaten  by  the 
Malays. 

Closely  allied  to  the  king-crabs  is  the  extinct  family  of  the 
Eurypterida^  an  example  of  which  is  figured  above  (Fig.  54). 
This  species  is  supposed  to  have  attained  a  length  of  probably 
six  feet,  but  other  forms  were  very  much  smaller. 


CRUSTACEA.  135 

ORDER  TRILOBITA.  —  The  Trilobites  constitute  another 
wholly  extinct  order  of  the  Crustacea,  and  deserve  a  short 
notice  from  their  great  geological  importance.  They  derive 
their  name  from  the  fact  that  the  body  exhibits  a  more  or  less 
conspicuous  division  into  a  central  and  two  lateral  lobes  (Fig. 
55,  1).  The  entire  shell  or  crust  is  composed  of  an  anterior 


FIG.  55.— Trilobita.    1.   Angelina  Sedgwickii;   2.  Diagram  of  the  cephalic  shield  of  a 
Trilobite  (after  Salter). 

semicircular  shield,  covering  the  head  (Fig.  55,  2),  a  series  of 
movable  rings,  constituting  the  thorax,  and  a  tail-piece  com- 
posed of  amalgamated  segments,  and  representing  the  abdo- 
men. On  the  under  surface  of  the  shell  nothing  had  ever 
been  discovered  except  the  upper  lip,  but  recently  traces  of 
limbs  have  been  made  out.  The  cephalic  shield  usually 
bears  a  pair  of  compound  eyes  (Fig.  55,  2  o),  but  these  are 
sometimes  wanting.  It  is  probable  that  most  of  the  Trilo- 
bites possessed  the  power  of  rolling  themselves  up  into  a  ball, 
much  as  our  modern  wood-lice.  The  Trilobrtes  are  only  known 
as  occurring  in  the  older  rocks  of  the  earth's  crust,  and  they 
are  chiefly  characteristic  of  the  period  known  to  geologists  as 
the  "  Silurian." 

ORDERS  CLADOCERA,  COPEPODA,  AND  OSTRACODA. — These 
orders  deserve  mention  more  from  the  extreme  abundance  of 
their  commoner  forms  than  for  any  other  reason.  They  in- 
clude a  number  of  minute  Crustaceans,  most  of  which  are 
commonly  called  "  water-fleas,"  and  abound  in  fresh  waters  in 
most  parts  of  the  world.  They  are,  however  so  small  that, 
though  visible  to  the  naked  eye,  they  can  only  be  satisfac- 
torily examined  under  the  microscope.  As  an  example  of  the 


136  INVERTEBRATE  ANIMALS. 

Cladocera  may  be  taken  the  "  branclied-horned  water-flea " 
(Daplinia  pulex,  Fig.  56,  #),  thousands  of  which  may  be 
captured  in  any  pond  in  summer.  In  this  pretty  little  species 
the  whole  body  is  enclosed  in  a  bivalve  shell,  which  is  so 
transparent  that  the  whole  organization  of  the  animal  is  clearly 
visible  through  it.  The  head  is  distinct,  and  carries  a  single 


FIG.  56.— Fresh   water  Entomostraca.    a  Cypris  iris  -  striata ;  5  DapTvnia  pulex; 
c  Cyclops  quadricomis. 


eye.  The  greater  antennas  are  branched.  The  males  are 
smaller  than  the  females,  and  much  fewer  in  number ;  and  it 
appears  to  be  a  well-established  fact  that  the  female,  when 
once  fertilized  by  the  male,  can  not  only  lay  eggs  for  the  rest 
of  her  life,  but  can  transmit  the  power  of  producing  fertile 
ova  to  her  young  for  several  generations.  Of  the  Copepoda 
one  of  the  commonest  is  the  Cyclops  (Fig.  56,  c),  in  which 
the  cephalo-thorax  is  covered  by  a  shield,  and  there  is  a  well- 
developed  abdomen.  The  female  carries  on  either  side  a  kind 
of  pouch  or  ovisac,  in  which  the  eggs  remain  till  they  are 
hatched.  The  little  Ostracoda  (Fig.  56,  a)  are  all  minute 
Crustaceans,  which  occur  in  both  fresh  and  salt  water.  They 
are  distinguished  by  the  fact  that  the  body  is  entirely  enclosed 
in  a  shell,  which  is  made  up  of  two  lateral  halves  or  valves. 
The  valves  of  the  shell  are  united  by  a  membrane  along  the 
back,  but  can  be  opened  below,  so  as  to  allow  of  the  protrusion 
of  the  feet. 

ORDER  CIRRIPEDIA. — The  last  order  of  Crustacea  which  re- 
quires mention  is  that  of  the  Cirripedia  (Lat.  cirrus,  a  curl ; 
and  peSj  foot),  comprising  the  so-called  barnacles  and  acorn- 


CRUSTACEA. 


137 


shells,  both  extremely  unlike  Crustaceans  to  look  at.  All  the 
Cirripedes  are  distinguished  by  the  fact  that,  while  they  are 
quite  free  when  young,  and  very  similar  to  some  of  the  little 
Crustaceans  just  described,  when  adult  they  are  immovably 
fixed  by  their  heads  to  some  solid  object.  In  this  fixed  con- 
dition the  body  and  internal  organs  are,  in  most  cases,  pro- 
tected by  means  of  a  calcareous  shell,  composed  of  many  pieces, 
and  the  only  part  of  the  body  which  remains  movable  is  the 
legs,  which  are  constantly  thrust  out  of  the  shell  and  again 
drawn  in  in  quest  of  food.  The  Cirripedia  were  formerly  de- 
scribed as  "multi valve"  shell-fish  (Molluscd),  owing  to  their 
possession  of  a  regular  calcareous  shell.  Two  distinct  types 
of  structure  are  known  among  the  Cirripedia  (Fig.  57),  con- 
stituting the  two  families  of  the  barnacles  (Lepadidce),  and 
the  acorn-shells  (Balanidce). 

In  the  barnacles  (Fig.  57,  #),  the  anterior  end  of  the  body 


FIG.  57.— Cirripedia.    a  Sessile  Cirripede  (Balanus) ;  5  Stalked  Cirripede  (Lepas). 


is  much  elongated,  and  is  converted  into  a  kind  of  stalk,  by 
means  of  which  the  animal  is  attached  to' some  solid  object, 
such  as  a  rock,  a  floating  log  of  timber,  or  even  some  marine 
animal.  In  the  acorn-shells  (Fig.  57,  a),  which  occur  in 
myriads  upon  every  solid  object  between  tide-marks,  there  is 
no  stalk,  but  the  head  is  firmly  cemented  to  the  centre  of  a 
membranous  or  shelly  plate.  The  body  is  enclosed  in  a  limpet- 
shaped  or  conical  shell,  composed  of  several  pieces,  and  having 
an  aperture  at  its  summit.  This  opening  is  closed  by  a  mov- 
able lid,  and  from  it  the  animal  can  protrude  its  delicate  legs 
or  "  cirri,"  which  look  like  a  "  glass  hand,"  and  are  constantly 
employed  in  sweeping  the  water  in  search  of  food. 

In  accordance  with  the  fixed  condition  of  the  adult,  almost 
all  the   Cirripedia  are  hermaphrodite,  possessing  both  male 


138  INVERTEBRATE  ANIMALS. 

and  female  organs  of  reproduction.  In  some  cases,  however, 
males  exist,  but  these  are  much  smaller  than  the  females,  and 
quite  different  to  them  in  appearance,  and  they  spend  their 
existence  within  the  shell  of  the  female. 

APPENDIX,  GIVING  THE  REMAINING  ORDERS  OP  CRUSTACEA. 

Order  Rhizocephala. — Minute  Crustaceans,  free  when  young,  but  when 
adult  parasitically  attached  to  the  abdomen  of  various  crabs.  When  adult 
they  are  completely  deformed,  destitute  of  limbs,  and  attached  to  their  host 
by  means  of  numerous  branched  tubes  or  roots  which  ramify  deeply  among 
the  internal  organs.  Ex.  Peltogaster. 

Order  Ichthyophthira. — Minute  Crustaceans,  free  when  young,  but  when 
adult  parasitic  upon  various  kinds  of  fishes ;  adult  usually  deformed  and 
soft ;  young  with  eyes  and  swimming-feet.  Ex.  Lerncea. 

Order  Phyllopoda. — Thoracic  feet  leaf-like  and  acting  as  branchiae.  Ex. 
Apus. 

Order  Lcemodipoda. — Eyes  sessile  ;  abdomen  rudimentary ;  respiration 
by  means  of  little  vesicles  attached  to  the  thoracic  segments  or  legs.  Ex. 
Cyamus  (the  whale-louse). 

Order  Amphipoda. — Eyes  sessile ;  abdomen  well  developed  ;  respiratory 
organs  in  the  form  of  vesicles  attached  to  the  thoracic  limbs.  Ex.  Sand- 
hopper  (  Talitrus)  \  Fresh-water  shrimp  ( Gammdrus). 

Order  Stomapoda. — Eyes  stalked ;  gills  unprotected,  usually  suspended 
beneath  the  abdomen.  Ex.  Locust-shrimp  (Squilla). 


CHAPTER  XV. 
AKACHNIDA. 

CLASS  II.  ARACHNID  A  (Gr.  Arachne,  a  spider). — This  class 
includes  the  mites,  ticks,  scorpions,  and  spiders,  and,  as  a 
whole,  is  very  nearly  related  to  the  preceding.  The  Arachnida, 
however,  are  distinguished  from  the  Crustacea  by  being  adapted 
in  most  cases  for  a  strictly  terrestrial  life,  so  that  when  any 
distinct  breathing-organs  are  present  these  are  never  in  the 
form  of  gills,  but  are  always  either  pulmonary  sacs  or  air- 
tubes  (tracheae).  In  none  of  the  Arachnida,  further,  are  there 
ever  more  than  four  pairs  of  legs,  and  the  segments  of  the  ab- 
domen never  carry  limbs  of  any  sort.  The  eyes  are  always 
sessile,  and  never  supported  upon  stalks ;  if  antennas  exist 
at  all,  they  are  much  modified,  and  the  head  is  always  amal- 
gamated with  the  thorax,  so  as  to  form  a  cephalo-thorax. 

The  integument  usually  produces  chitine  more  or  less 
abundantly,  so  as  to  constitute  a  resistent  shell ;  but  in  some 
cases  the  skin  remains  permanently  soft.  The  mouth  is  situated 
in  the  anterior  portion  of  the  body,  and  in  the  higher  forms  is 
furnished  with  a  pair  of  prehensile  jaws,  called  "  mandibles," 
a  pair  of  chewing-jaws,  called  "  maxillae,  and  a  lower  lip.  In 
the  scorpions  an  upper  lip  is  present  as  well.  In  the  true 
spiders  each  mandible  terminates  in  a  sharp  movable  hook, 
perforated  by  a  canal  which  communicates  with  a  poison-gland 
situated  near  its  base.  By  means  of  this  poisonous  fluid  the 
spiders  kill  such  animals  as  they  capture.  In  the  scorpions 
the  mandibles  are  short,  and  terminate  in  strong  pincers.  In 
them,  too,  the  maxillas  are  furnished  with  enormously-de- 
veloped nipping-claws  or  chelae.*  In  all  the  Arachnida  the 
mandibles  are  believed  to  correspond  to  the  antenna3  of  the 

*  These  nipping-claws  in  the  scorpions  are  produced  not  by  the  maxillae  themselves,  but 
by  two  appendages  to  the  maxillae,  which  are  known  as  "  maxillary  palpi." 


140  INVERTEBRATE  ANIMALS. 

Crustacea.  In  the  lower  Arachnida^  such  as  the  ticks,  the 
organs  of  the  mouth  are  modified  to  enable  them  to  imbibe 
fluids. 

The  mouth  in  the  Arachnida  opens  into  a  pharynx,  which 
is  of  extraordinarily  small  diameter  in  the  true  spiders,  which 
live  simply  on  the  juices  of  their  prey.  The  intestinal  canal 
is  usually  short  and  straight,  and  is  continued  without  convo- 
lutions to  the  aperture  of  the  anus.  Salivary  glands  are  also 
present,  as  well  as  ramified  tubes  which  are  believed  to  act  as 
kidneys. 

The  circulation  is  maintained  by  means  of  a  dorsal  heart, 
which  is  situated  above  the  alimentary  canal.  All  the  Arach- 
nida breathe  air  directly,  and  the  function  of  respiration  is 
performed  by  the  general  surface  of  the  body  (as  in  the  lowest 
members  of  the  class),  or  by  branched  air-tubes  termed  "tra- 
cheae," or  by  distinct  pulmonary  chambers  or  sacs,  or,  lastly, 
by  a  combination  of  tracheae  with  pulmonary  sacs.  The  tra- 
cheae are  essentially  similar  in  structure  and  function  to  the 
breathing-tubes  of  the  Myriapoda  and  Insecta,  and  consist  of 
tubes,  which  open  on  the  surface  of  the  body  by  distinct  aper- 
tures called  "  spiracles."  The  walls  of  the  tube  are  prevented 
from  collapsing  by  means  of  a  spirally-coiled  thread  or  filament 
of  chitine,  which  is  wound  round  their  walls  within  their  inner 
lining.  The  pulmonary  sacs  which  occur  in  the  Arachnida 
are  simple  chambers  formed  by  an  inversion  of  the  skin,  which 
constitutes  a  number  of  closely-set  plates  or  folds.  The  whole 
of  the  interior  of  the  pulmonary  sacs  is  richly  supplied  with 
blood,  and  air  is  admitted  by  means  of  minute  external  open- 
ings. 

The  nervous  system  is  of  the  regular  articulate  type,  but 
the  ganglia  of  the  ventral  chain  are  often  massed  together  in 
particular  situations.  In  no  case  are  compound  eyes  present; 
and,  when  distinct  organs  of  vision  exist,  these  are  in  the  form 
of  from  two  to  eight  simple  eyes. 

ORDERS  OF  THE  ARACHNIDA. 

ORDER  I.  PODOSOMATA. — In  this  order  are  included  the 
"  Sea-spiders,"  which  are  wholly  marine,  and  were  long  be- 
lieved to  be  referable  to  the  Crustacea  on  this  account.  As 
they  have  no  respiratory  organs  of  any  kind,  the  question  can- 
not be  definitely  settled,  but  they  have  no  more  than  four 
pairs  of  legs,  and  would  therefore  seem  to  be  properly  refer- 
able to  the  Arachnida.  In  some  forms  the  legs  attain  an  ex- 


ARACHNIDA.  141 

traordinary  length,  and  contain  prolongations  from  the  stom- 
ach. They  are  all  grotesque-looking  animals,  found  at  low 
water  upon  stones  or  marine  plants,  or  parasitically  attached 
to  marine  animals.  One  of  the  commonest  forms  is  figured 
below  (Fig.  5Yi,  a). 

ORDER  II.  ACARINA. — The  most  familiar  members  of  this 
order  are  the  Mites  and  Ticks  (Fig.  57^,  #,  c).  They  are  dis- 
tinguished by  the  fact  that  the  abdomen  is  amalgamated  with 
the  cephalo-thorax  to  form  a  single  mass.  Respiration  is  ef- 
fected by  the  general  surface  of  the  body  or  by  air-tubes 
(tracheae). 

The  habits  of  the  mites  are  extremely  varied.  Some  are 
found  upon  different  plants  (Fig.  57|-,  b)  ;  others  are  parasitic 
upon  water-insects  when  young,  but  swim  about  freely  when 
adult  (Fig.  57J,  c) ;  others  are  permanently  parasitic  upon 


FIG.  57X-— Arachnida.     a  Pycnofjonum  littorale;  b  Tetranyclms  telariw,  one  of  the 
"Sociable"  rnites;  c  Hydrachna  globulus,  one  of  the  "Water-mites." 

other  animals,  such  as  sheep,  dogs,  insects,  etc. ;-  and  others 
inhabit  decaying  provisions,  as  is  the  case  with  the  well-known 
"  cheese-mite  "  (Acarus  domesticus).  Two  species  have  a  con- 
siderable medical  interest  as  attacking  man.  One  of  these 
causes  the  skin-disease  which  is  known  as  the  "  itch,"  and  the 
other  is  found  inhabiting  certain  glandular  follicles  of  the 
skin,  probably  without  an  exception  even  in  favor  of  the  most 
cleanly  people. 

ORDER  III.  PEDIPALPI. — In  this  family  are  the  most  for- 
midable of  all  the  Arachnida — namely,  the  Scorpions.  They 
are  all  distinguished  by  the  fact  that  the  abdomen  is  divided 
into  distinct  segments,  and  is  continued  into  the  cephalo- 
thorax  without  any  well-marked  boundary  or  constriction.  In 


142  INVERTEBRATE  ANIMALS. 

the  true  scorpions  the  end  of  the  abdomen  (Fig.  58)  is  com- 
posed of  a  hooked  telson,  which  is  perforated  for  the  duct  of  a 
poison-gland,  situated  at  its  base.  It  is  by  means  of  this  that 
the  scorpions  sting ;  and  the  poisonous  fluid  which  they  secrete 


FIG.  58.— Scorpion  (reduced). 

is  sufficiently  powerful  to  render  their  wounds  troublesome 
and  painful,  if  not  positively  dangerous.  The  mandibles  in 
the  scorpions,  as  already  said,  are  developed  into  pincers,  and 
the  so-called  "  maxillary  palpi "  constitute  powerful  nipping- 
claws.  The  respiratory  organs  are  in  the  form  of  pulmonary 
sacs,  four  on  each  side,  opening  on  the  under  surface  of  the 
abdomen  by  as  many  distinct  apertures  or  spiracles. 

The  scorpions  live  in  the  warmer  regions  of  the  temperate 
zone  and  in  tropical  countries,  and  are  generally  found  hiding 
under  stones  or  in  crevices  of  walls.  Their  sting,  though 
much  exaggerated,  is  certainly  capable  of  producing  very  un- 
pleasant symptoms.* 

ORDER  IV.  ARANEIDA. — In  this  order  are  the  true  Spiders, 
readily  distinguished  from  the  insects,  with  which  they  are 
popularly  confounded,  by  having  four  pairs  of  legs,  as  well  as 
by  other  characters.  In  all  the  true  spiders  (Fig.  59)  the  seg- 
ments of  the  thorax  and  head  are  united  to  form  a  single  mass 
or  cephalo-thorax,  to  which  the  soft  and  unsegmented  ab- 
domen is  joined  by  a  constricted  stalk,  or  neck.  Respiration 
is  effected  by  means  of  pulmonary  sacs,  usually  conjoined  with 
tracheae.  The  pulmonary  sacs  are  two  or  four  in  number,  and 
open  on  the  surface  of  the  abdomen  by  as  many  apertures. 

*  Nearly  allied  to  the  Scorpions  are  the  so-called  "  Harvest-spiders11  (Phalangidce),  and 
the  diminutive  "Book-scorpion"  (CheUfer\  which  is  commonly  to  be  found  among  old 
books. 


ARACHNID  A.  143 

The  head  bears  from  six  to  eight  simple  eyes ;  the  mandibles 
are  hooked,  and  carry  the  duct  of  a  poison-gland;  and  the 
maxillary  palpi  are  not  developed  into  nipping-claws.  The 
spiders  are  all  predaceous  and  rapacious  animals,  and  many  of 


FIG.  59.— Araneida.     Theridion  riparian  (female). 

them  possess  the  power  of  constructing  webs,  either  for  the 
capture  of  their  prey,  or  simply  for  lining  their  habitations. 
For  the  production  of  the  web,  spiders  are  furnished  with 
special  glands,  situated  at  the  extremity  of  the  abdomen.  The 
secretion  of  these  glands  is  a  viscid  fluid,  which  hardens  rapid- 
ly on  exposure  to  air,  and  which  is  cast  into  its  proper  thread- 
like shape  by  passing  through  what  are  called  the  "spin- 
nerets." These  are  little  conical  or  cylindrical  organs  placed 
at  the  end  of  the  abdomen,  and  perforated  by  a  number  of  ex- 
tremely minute  tubes,  through  which  the  secretion  of  the 
glands  has  to  pass  before  reaching  the  air.  Many  spiders, 
however,  do  not  construct  any  web,  unless  it  be  for  their  own 
habitations,  but  simply  hunt  their  prey  for  themselves. 

The  spiders  are  oviparous,  and  their  young  pass  through 
no  metamorphosis,  but  they  cast  their  skin,  or  "  moult,"  re- 
peatedly before  they  attain  the  size  of  the  adult. 


CHAPTER  XVI. 
MYRIAPODA. 

CLASS  III.  MYEIAPODA  (Gr.  murios,  countless;  podes, 
feet). — This  class  is  an  extremely  small  one,  and  includes  only 
the  Centipedes  and  the  Millipedes.  In  all  the  Myriapoda  the 
head  is  distinct,  and  not  amalgamated  with  the  thorax.  There 
is  no  clear  boundary-line  between  the  thorax  and  the  ab- 
domen, both  being  composed  of  nearly  similar  segments.  The 
body,  with  one  exception,  always  consists  of  more  than  twenty 
rings,  and  the  hinder  segments,  which  correspond  to  the  ab- 
domen, always  carry  locomotive  appendages,  whereas  the 
abdominal  rings  in  Arachnida  and  Insecta  are  always  des- 
titute of  locomotive  appendages.  One  pair  of  antennce  is 
present,  and  the  number  of  the  legs  is  always  more  than  eight 
pairs.  Respiration  is  carried  on  by  branched  air-tubes  or 
tracheae. 

In  most  of  their  characters  the  Myriapoda  closely  re- 
semble the  true  insects,  with  which,  indeed,  they  are  not  un- 
commonly classed.  The  true  insects,  however,  always  have 
the  head,  thorax,  and  abdomen,  distinct  from  each  other,  and 
have  never  more  than  three  pairs  of  legs.  In  most  of  the 
Myriapoda  the  young,  or  "  larvae,"  are  more  like  insects  than 
the  adult,  since  they  have  only  three  pairs  of  legs,  or  are  alto- 
gether destitute  of  feet.  In  some  cases,  however,  the  young 
Myriapod,  on  escaping  from  the  egg,  possesses  nearly  all  the 
characters  of  the  parents,  except  that  the  number  of  body- 
rings,  and  consequently  of  legs,  is  smaller,  and  increases  with 
every  change  of  skin  ("  moult ").  The  class  is  divided  into 
two  leading  families,  represented  by  the  common  Centipedes 
and  Millipedes. 

The  Centipedes  (Fig.  60)  are  carnivorous  in  their  habits, 
and  the  organs  of  the  mouth  are  adapted  for  a  life  of  rapine. 


MYRIAPODA. 


145 


In  addition  to  the  parts  of  the  mouth  proper,  they  have  two 
pairs  of  "  foot-jaws,"  of  which  the  second  is  hooked  and  per- 
forated for  the  'discharge  of  a  poisonous  fluid.  The  bite  of  the 
common  European  species  is  perfectly  harmless  to  man,  but 
some  of  the  tropical  forms  attain  a  length  of  a  foot  or  more, 
and  are  consequently  able  to  inflict  extremely  severe  and  even 


FIG.  CO.— Centipede  (Scolopendrci). 


dangerous  bites.  The  true  centipedes  are  further  distinguished 
by  the  number  of  legs  not  being  indefinitely  great  (usually 
from  fifteen  to  twenty  pairs),  and  by  the  fact  that  the  antennae 
are  composed  of  not  less  than  fourteen  joints  each. 

The  Millipedes  (Fig.  61)  are  repulsive-looking  but  perfectly 


FIG.  61.— Millipede  (lulus). 

innocent  animals,  which  feed  principally  upon  decaying  vege- 
table matter.  The  body,  in  the  ordinary  millipedes,  is  round- 
ed and  worm-like,  and  the  segments  are  so  amalgamated  that 
each  apparent  body-ring  gives  origin  to  two  pairs  of  minute, 
thread-like  feet.  The  mouth  is  destitute  of'  the  powerful  jaws 
which  are  found  in  the  centipedes,  the  legs  are  indefinitely 
numerous,  and  the  antennae  are  short,  and  are  composed  of  no 
more  than  six  or  seven  joints  each. 

The  European  millipedes  are  all  of  small  size,  but  an  Amer- 
ican species  is  stated  to  attain  a  length  of  more  than  half  a  foot. 

A  third  family  has  been  established  for  a  curious  little 
creature  called  Pauropus.  In  this  the  body  consists  of  only 
ten  segments,  and  there  are  no  more  than  nine  pairs  of  legs. 
The  antennae  are  five-jointed,  forked,  and  provided  with  jointed 
appendages.  There  are  no  tracheae,  and  respiration  is  carried 
on  by  the  skin.  It  is  very  .small,  and  is  found  inhabiting 
decayed  leaves  and  damp  situations. 


CHAPTER  XVII. 
INSECTA. 

CLASS  IV.  INSECTA. — The  true  Insects  are  distinguished 
from  the  preceding  classes  of  articulate  animals  by  the  fact 
that  the  three  divisions  of  the  body,  namely,  the  head,  thorax, 
and  abdomen,  are  always  distinct  from  one  another  /  there 
are  never  more  than  three  pairs  of  legs  in  the  adult,  and  these 
are  borne  upon  the  thorax  ;  the  abdomen  is  destitute  of  loco- 
motive appendages.  Respiration  is  effected  by  means  of  air- 
tubes  or  tracheae,  and,  in  most  insects,  two  pairs  of  wings  are 
developed  from  the  back  of  the  second  and  third  segments  of 
the  thorax. 

The  integument  in  insects  is  more  or  less  hardened  by 
the  deposition  of  chitine  in  it,  and  the  body  is  deeply  cut  into 
segments — hence  the  name  Insect  (from  the  Latin  insectus,  cut 
into).  The  head  in  insects  (Fig.  62,  a)  is  composed  of  several 
segments  amalgamated  together,  and  carries  a  pair  of  jointed 
feelers  or  antennae,  a  pair  of  eyes,  usually  compound,  and  the 
appendages  of  the  mouth.  The  thorax  in  insects  (b,  c,  d)  is 
composed  of  three  segments,  which  are  amalgamated  together, 
but  are  generally  pretty  easily  recognized.  Each  of  these 
segments  of  the  thorax  carries,  in  perfect  insects,  a  single 
pair  of  jointed  legs,  so  that  there  are  three  pairs  in  all.  To 
the  back  of  the  two  hinder  segments  of  the  thorax,  in  most 
insects,  there  are  also  attached  two  pairs  of  wings.  In  their 
typical  form,  the  wings  are  membranous  expansions,  supported 
by  more  or  less  numerous  hollow  tubes,  known  as  the  "  nerv- 
ures."  One  or  both  pairs  of  wings  may  be  wanting,  and 
when  all  are  present  the  anterior  pair  may  be  much  modified 
by  the  deposition  of  chitine  in  it.  These  modifications  will 
be  treated  of  in  speaking  of  the  orders  of  insects.  The  abdo- 
men in  insects  (e)  is  properly  composed  of  nine  segments, 


INSECTA. 


147 


FIG.  62. — Diagram  of  the  external  anatomy  of  an  insect:  a  Head,  carrying  tho  eyes  and 
antennae ;  b  First  segment  of  the  thorax,  with  the  first  pair  of  legs ;  c  Second  segment 
of  the  thorax,  with  the  second  pair  of  legs  and  the  first  pair  of  wings ;  d  Third  seg- 
ment of  the  thorax,  with  the  third  pair  of  legs  and  the  second  pair  of  wings ;  e  Abdo- 
men, without  limbs,  but  carrying  terminal  appendages  concerned  in  reproduction. 

which  are  usually  more  or  less  freely  movable  upon  one  an- 
other, and  which  never  carry  locomotive  limbs,  as  is  so  com- 
monly the  case  in  the  Crustacea.  The  extremity  of  the  abdo- 
men is,  however,  often  furnished  with  appendages  which  are 
primarily  connected  with  reproduction,  but  which  are  often 
converted  into  weapons  of  offence  and  defence.  Of  this 
nature  are  the  "  ovipositors "  of  ichneumons,  the  stings  of 
bees  and  wasps,  and  the  forceps  of  the  common  earwig. 

The  organs  of  the  mouth  in  insects  require  a  brief  consid- 
eration, as  being  in  the  closest  possible  relation  with  their 
habits  and  mode  of  life.  Two  chief  types  of  mouth  are  recog- 
nizable in  insects,  termed  respectively  the  "  masticatory  "  and 
"  suctorial,"  according  as  the  mouth  is  fitted  for  biting  and 
chewing,  or  simply  for  imbibing  fluids.  The  masticatory 
mouth  is  seen  in  perfection  in  the  beetles,  in  which  the  follow- 
ing organs  are  present :  1.  An  upper  lip  or  "  labrum "  at- 
tached below  the  front  of  the  lead.  2.  A  pair  of  biting-jaws 


148 


INVERTEBRATE  ANIMALS. 


or  "  mandibles."  3.  A  pair  of  chewing-jaws  or  "  maxillae " 
provided  with  jointed  filaments,  called  the  "  maxillary  palpi." 
4.  A  lower  lip  or  "labium"  which  also  carries  a  pair  of 
jointed  filaments,  known  as  the  "  labial  palpi."  In  the  typical 
suctorial  mouth,  as  seen  in  the  butterflies  and  moths,  the  fol- 
lowing is  the  arrangement  of  parts  :  The  upper  lip  and  man- 
dibles are  quite  rudimentary ;  the  maxillae  are  greatly  length- 
ened, and  form  a  spiral  tube  fitted  for  sucking  up  the  juices  of 
flowers ;  and  the  labial  palpi  are  much  developed,  and  form 
two  hairy  cushions  between  which  the  trunk  can  be  coiled  up 
when  not  in  use.  In  many  insects,  the  organs  of  the  mouth 

are  essentially  adapted  for  suc- 
tion, but  are  also  fitted  for  pierc- 
ing solid  substances,  such  as  the 
skin  of  animals  or  the  stems  of 
plants.  In  these  the  lower  lip 
forms  a  kind  of  sucking-tube  or 
sheath,  within  which  are  con- 
tained the  maxillae  and  mandi- 
bles, which  are  modified  so  as 
to  form  piercing  organs  or  lan- 
cets. In  the  common  bee,  the 
masticatory  and  suctorial  types 
of  mouth  are  combined.  The 
mandibles  or  biting-jaws  are  re- 
tained, to  enable  the  honeycomb 
to  be  manufactured,  and  there 
is  also  a  tubular  trunk  fitted  for 
sucking  up  the  juices  of  flowers. 
In  the  butterflies,  too,  in  which 
the  mouth  of  the  adult  is  strict- 
ly adapted  for  suction,  the  cater- 
pillar is  furnished  with  a  mas- 
ticating mouth,  so  that  it  can 
feed  upon  leaves  or  other  solid 
substances. 

The  mouth  in  the  mastica- 

SUseS''7'111^116^010^^  ting  Insects  (Fig.  63,  a)  leads 

into  a   membranous  and  often 

folded  cavity,  termed  the  "crop"  (#),  from  which  the  food 
passes  to  a  second  muscular  cavity  or  "gizzard"  (c).  The 
gizzard  is  adapted  for  crushing  the  food,  and  often  has  plates 
or  teeth  of  chitine  developed  in  its  walls.  It  is  succeeded 
by  the  true  digestive  cavity  (d),  which  is  termed  the  "  chy- 


FIG.  63.— Digestive  apparatus  of  a  Beetle 
(Carabm  auratus).  a  Gullet;  b  Crop; 
c  Gizzard;  d  Chylific  stomach;  e  Mal- 


INSECT  A.  149 

lific  stomach."  From  this  there  proceeds  an  intestine  (/*), 
of  variable  length,  which  usually  terminates  in  a  chamber  (g) 
called  the  "  cloaca  "  (Lat.  cloaca,  a  sink),  into  which  the  ducts 
of  the  reproductive  organs  open.  The  commencement  of 
the  gullet  is  furnished  with  glandular  appendages,  which  are 
believed  to  discharge  the  functions  of  salivary  glands.  Imme- 
diately behind  the  posterior  aperture  of  the  stomach  are  a 
variable  number  of  caecal  convoluted  tubes  (e),  which  are 
known  as  the  "  Malpighian  vessels,"  after  their  discoverer  Mal- 
pighi,  and  which  are  generally  looked  upon  as  representing  the 
liver.  Close  to  the  cloaca  may  be  other  tubes,  which  are  be- 
lieved, from  their  position,  to  exercise  the  functions  of  kid- 
neys (A). 

The  circulation  in  insects  is  mainly  carried  on  by  a  long, 
contractile  tube,  placed  along  the  back,  and  termed  the  "  dor- 
sal vessel."  The  blood,  collected  from  the  various  tissues  and 
organs  of  the  body,  enters  the  dorsal  vessel  from  behind,  and 
is  driven  forward  to  the  anterior  extremity  of  the  body.  Res- 
piration is  effected  by  means  of  air-tubes  or  tracheae,  which 
commence  at  the  surface  by  so  many  apertures  or  spiracles, 
and  branch  repeatedly  as  they  proceed  inward  through  the 
tissues.  They  have  essentially  the  same  structure  as  in  the 
Arachnida,  consisting  of  membranous  tubes  strengthened  by 
means  of  a  spirally-coiled  filament  of  chitine. 

The  nervous  system  in  insects,  though  sometimes  some- 
what modified,  has  essentially  the  regular  annulose  form  of  a 
ventral  chain  of  ganglia,  traversed  in  front  by  the  gullet.  The 
organs  of  sense  are  the  eyes  and  antennae.  The  eyes  are 
usually  "  compound,"  and  are  composed  of  numerous  six-sided 
lenses,  united  together,  and  each  supplied  by  a  separate  ner- 
vous filament.  As  many  as  eight  thousand  of  these  lenses 
have  been  counted  in  one  of  the  eyes  of  the  common  cock- 
chafer, and  this  number  is  sometimes  greatly  exceeded.  Be- 
sides these  compound  eyes  there  are  sometimes  "simple" 
eyes,  identical  in  structure  with  the  single  lenses  of  the  com- 
pound eyes ;  and  in  rare  cases  these  are  the  only  organs  of 
vision.  The  feelers  or  antennae,  with  which  all  insects  are 
furnished,  are  jointed  filaments  attached  close  to  the  eyes,  and 
assuming  very  different  shapes  in  different  insects.  They  ap- 
pear to  be  certainly  organs  of  touch,  but  they  very  probably 
minister  to  other  senses  as  well,  and  there  is  some  reason  to 
suppose  that  they  are  connected  with  the  sense  of  hearing  in 
particular. 

The  sexes  in  insects  are  distinct,  and  most  of  them  are 


150  INVERTEBRATE  ANIMALS. 

oviparous.  Generally  speaking,  the  young  insect  is  extremely 
different  in  external  character  from  the  adult,  and  it  requires, 
before  reaching  maturity,  to  pass  through  a  series  of  changes 
which  collectively  constitute  what  is  called  the  "metamor- 
phosis. In  some  insects,  however,  there  is  no  proper  meta- 
morphosis, and  in  some  the  changes  which  take  place  are  not 
so  complete  and  striking  as  in  others.  By  the  absence  of  met- 
amorphosis, or  by  its  completeness  Avhen  present,  insects  are 
divided  into  three  convenient,  though  perhaps  not  strictly 
natural,  sections,  as  follows : 

Section  I.  Ametabolic  Insects. — The  insects  belonging  to 
this  section  are  said  to  be  "Ametabolic"  (Gr.  a,  without; 
vnetabole^  change),  because  they  pass  through  no  metamorpho- 
sis. The  young,  on  their  escape  from  the  egg,  resemble  the 
adult  in  every  respect  except  in  size,  and  they  undergo  110 
alteration  in  reaching  maturity,  except  that  they  grow  larger. 
All  the  insects  of  this  section  are  destitute  of  wings  in  the 
adult  state,  and  they  are  therefore  often  called  "Aptera" 
(Gr.  a,  without ;  pteron,  a  wing). 

Section  II.  Ilemimetabolic  Insects. — In  the  insects  be- 
longing to  this  section  (Gr.  hemi,  half;  and  metabole,  change), 
there  is  a  metamorphosis  consisting  of  three  stages,  but  these 
stages  do  not  differ  much  from  one  another  in  appearance. 
The  young,  on  escaping  from  the  egg,  is  known  as  the  "  larva," 
and  it  is  not  only  much  smaller  than  the  adult,  but  is  desti- 
tute of  wings.  After  several  changes  of  skin,  the  larva  enters 
into  the  second  stage,  when  it  is  termed  the  "pupa."  The 
pupa  is  active  and  locomotive,  and  rarely  differs  much  from 
the  larva,  except  that  it  is  bigger,  and  rudimentary  wings 
have  now  appeared  on  the  back  of  the  thorax.  After  a  cer- 
tain period,  and  after  some  changes  of  skin,  the  wings  burst 
from  their  sheaths,  and  the  pupa  is  now  converted  into  the 
third  and  final  stage,  when  it  is  known  as  the  "  imago "  or 
perfect  insect.  In  all  the  insects  belonging  to  this  section — 
such  as  grasshoppers,  dragon-flies,  etc. — the  second  stage  or 
pupa  is  active  and  locomotive ;  and  for  this  reason  the  meta- 
morphosis is  said  to  be  "  incomplete.' 

Section  III.  Holometabolic  Insects  (Gr.  holos,  entire ;  and 
metabole,  change). — The  insects  belonging  to  this  section — 
such  as  butterflies,  moths,  and  beetles — pass  through  three 
stages,  just  as  do  the  preceding,  but  these  stages  differ  from 


INSECTA. 


151 


motive  feet,  which  do  not  correspond  with  the  three  pairs  proper 
to  the  adult  (see  Fig.  71,  #),  though  these  are  usually  present 
as  well.  The  larva  is  also  provided  with  masticating  organs, 


FIG.  64. — Metamorphosis  of  the  Magpie-moth  (Phalcena  grossulariata). 


and  eats  voraciously.  In  this  stage  of  the  metamorphosis,  the 
larvae  constitute  what  are  popularly  known  as  "  caterpillars  " 
or  "  grubs."  Having  remained  in  this  condition  for  a  longer 
or  shorter  time,  and  having  undergone  repeated  changes  of 
skin,  necessitated  by  its  rapid  growth,  the  larva  passes  into 
the  second  stage,  and  becomes  a  pupa  (Fig.  64 — see  also  Fig. 
71).  In  this  stage  the  insect  remains  quiescent,  unless  irri- 
tated, and  it  is  very  often  attached  to  some  foreign  object,  so 
as  to  be  quite  incapable  of  changing  its  place.  In  the  case 
of  the  butterflies  and  moths,  the  pupa  constitutes  what  is  so 
familiarly  known  as  the  "  chrysalis."  The  body  is  protected 
by  a  chitinous  pellicle,  and  in  some  cases  this  is  still  further 
protected  by  the  dried  skin  of  the  larva ;  while  in  other  cases 
the  larva — immediately  before  entering  the  pupa  stage — spins 


152  INVERTEBRATE  ANIMALS. 

for  itself  a  protective  case  of  silken  threads,  which  surrounds 
the  chrysalis,  and  is  known  as  the  "  cocoon."  Having  re- 
mained for  a  variable  time  in  this  inanimate,  quiescent  pupa- 
stage,  during  which  rapid  changes  have  been  going  on  in  the 
interior  of  the  animal,  the  insect  now  frees  itself  from  the  en- 
velope which  obscured  it,  and  appears  as  the  perfect  winged 
adult  or  imago. 


CHAPTER  XVIII. 
ORDERS    OF    INSECTS. 

THE  known  number  of  insects  is  so  enormous,  their  forms 
are  so  various,  and  their  habits  and  instincts  are  not  only  so 
remarkable  but  have  been  so  fully  described,  that  it  were 
hopeless  to  attempt  here  to  do  more  than  give  the  briefest 
possible  outline  of  the  leading  characters  which  distinguish 
the  different  orders.  The  student  desirous  of  further  informa- 
tion on  this  head  must  have  recourse  to  treatises  specially  de- 
voted to  entomology. 

SECTION  I.  AMETABOLIC  INSECTS.  —  Young  not  passing 
through  a  metamorphosis ,  and  differing  from  the  adult  in 
size  only.  Perfect  insect  (imago)  destitute  of  wings;  eyes 
simple,  sometimes  wanting. 

ORDER  I.  ANOPLURA  (Gr.  anoplos,  unarmed ;  our  a,  tail). 
— The  insects  comprised  in  this  order  are  parasitic  upon  man 
and  other  animals,  and  they  are  commonly  known  as  Lice. 
They  are  all  very  minute  in  size,  destitute  of  wings  in  the 
adult  state,  having  a  mouth  formed  for  suction,  and  having 
either  two  simple  eyes  or  none. 

ORDER  II.  MALLOPHAGA  (Gr.  m,allos,  a  fleece ;  phago,  I 
eat). — These  are  known  as  "Bird-lice,"  and  are  all  minute 
parasites  on  different  birds.  They  are  distinguished  from  the 
true  lice  by  not  living  upon  the  juices  of  their  host,  but  upon 
the  more  delicate  and  tender  appendages  of  the  skin.  The 
mouth  is,  consequently,  not  suctorial,  but  fitted  for  biting. 

ORDER  III.  THTSANURA  (Gr.  thusanoi,  fringe  ;  oura,  tail). 
— The  most  familiar  members  of  this  order  are  the  "  Spring- 


154  INVERTEBRATE  ANIMALS. 

tails"  (Podurce),  which  are  commonly  found  under  stones  or 
in  cellars  and  such  like  situations.  They  are  distinguished  by 
having  the  extremity  of  the  abdomen  furnished  with  bristles, 
by  the  sudden  straightening  of  which  the  insect  can  effect  pow- 
erful leaps.  In  many  cases  the  body  is  covered  with  delicate 
scales  which  form  beautiful  objects  under  high  powers  of  the 
microscope. 

SECTION  II.  HEMIMETABOLIC  INSECTS.  —  Metamorphosis 
incomplete  ;  the  larva  differing  from  the  perfect  insect  chiefly 
in  the  absence  of  wings  and  in  size  ;  pupa  usually  active,  or, 
if  quiescent,  capable  of  movement. 

ORDER  IV.  HEMIPTERA  (Gr.  hemi,  half;  pteron,  wing). — 
In  this  order  the  mouth  is  formed  for  suction ;  the  eyes  are 
compound,  but  simple  eyes  are  often  present  in  addition.  Two 
pairs  of  wings  are  always  present. 

The  Hemiptera  live  upon  the  juices  of  plants  or  animals, 
which  they  are  enabled  to  obtain  by  means  of  their  suctorial 
mouths.  All  the  four  wings  are  generally  present,  but  the 
condition  of  these  varies  in  different  sections  of  the  order.  In 
one  group  all  the  four  wings  are  membranous  (Fig.  65) ;  but 
in  the  other  the  posterior  wings  and  the  tips  of  the  anterior 


FIG.  65.— Hemiptera.    Bean  Aphis  (Aphis  fabce) ;  winged  male  and  wingless  female. 

wings  alone  are  membranous.  The  inner  portions  of  the  an- 
terior wings  are  hardened  by  chitine,  and  they  are  known  as 
"hemelytra"  (Gr.  hemi,  half;  and  elutron,  a  sheath).  Among 
the  more  familiar  examples  of  the  Hemiptera  are  the  numer- 
ous species  of  Plant-lice  (Aphides),  the  Field-bug  (Penta- 
toma),  the  Boat-fly,  the  Cochineal  insects,  and  the  Cicadas. 

The  Cochineal  insects  are  of  considerable  commercial  im- 
portance, as  the  dried  and  powdered  bodies  of  the  female  con- 
stitute the  substance  known  as  Cochineal,  from  which  is  ob- 


ORDERS  OF  INSECTS. 


155 


tained  the  brilliant  pigment  carmine.  The  male  insect  is 
winged,  and  is  smaller  than  the  female,  which  is  wingless. 
They  live  upon  different  species  of  Cactus  ( Opuntia,)  and  are 
mainly  imported  from  Mexico,  Algeria,  and  the  Canary  Islands. 
Numerous  species  of  Aphides  or  Plant-lice  (Fig.  65)  are 
known,  and  they  are  among  the  greatest  pests  of  the  gar- 
dener and  farmer,  as  they  are  extraordinarily  prolific,  and  live 
upon  the  juices  of  plants.  One  of  the  most  curious  points 
about  the  Plant-lice  is  that  they  secrete  a  sweet  and  sticky 
fluid,  which  is  expelled  from  the  body  by  two  little  tubular 
filaments  placed  near  the  end  of  the 

abdomen.    Ants  are  excessively  fond        \  / 

of  this  fluid,  and  hunt  after  Aphides 
in  all  directions  in  order  to  ob- 
tain it ;  and  it  is  a  well-established 
fact  that  the  Plant-lice  are  actually 
pleased  with  this,  and  voluntarily 
yield  up  the  coveted  fluid  to  the 
importunity  of  the  ants. 

ORDER  V.  ORTHOPTERA  (Gr.  or- 
thos,  straight ;  pteron,  wing). — The 
mouth  in  this  order  is  strictly  masti- 
catory ;  there  are  four  wings  present 
in  most,  but  the  anterior  pair  is 
smaller  than  the  posterior,  and  of  a 
different  texture.  The  posterior 
wings  are  membranous,  and  are  fold- 
ed lengthwise,  like  a  fan  ;  the  ante- 
rior wings  are  leathery,  and  consti- 
tute cases  for  the  posterior  wings 
(elytra).  This  order  includes  the 
Crickets  (Achetina),  Grasshoppers 
(Gryllina))  Locusts  (Locustind), 
Cockroaches  (Blattina,  Fig.  66), 
and  others.  Some  of  them  are 
formed  for  running,  all  the  legs 
being  nearly  equal  in  size ;  others 
have  the  first  pair  of  legs  greatly  developed,  and  constituting 
powerful  organs  of  prehension ;  while  others,  such  as  the  Lo- 
custs and  Grasshoppers,  have  the  hindmost  pair  of  legs  much 
longer  than  the  others,  giving  them  a  considerable  power  of 
leaping.  All  the  Orthoptera  are  extremely  voracious,  and 
every  one  is  acquainted  with  the  terrible  ravages  occasionally 
caused  in  hot  countries  by  swarms  of  locusts. 


FIG.  66. — Orthoptera.  The  com- 
mon Cockroach  (Blatta  ori&iita- 
Us\  male  and  female. 


156  INVERTEBRATE  ANIMALS. 

The  most  destructive  species  is  the  Migratory  Locust 
(Acrydium  migratorium,  Fig.  67),  which  is  very  abundant  in 
Africa,  India,  and  throughout  the  whole  of  the  East.  Owing 
to  the  rapidity  with  which  they  devour  every  thing  they  can 
possibly  eat,  and  owing  to  their  enormous  numbers,  the  Lo- 
custs are  compelled  to  be  constantly  on  the  move,  looking  for 
"  fresh  fields  and  pastures  new."  It  is  from  these  migrations 


FIG.  67.— The  Migratory  Locust  (Acrydium  migratorium). 

in  vast  bodies  in  search  of  food  that  the  Migratory  Locust 
takes  its  name.  When  one  of  these  destructive  hosts  visits 
a  district,  it  only  needs  a  few  hours  to  convert  the  most  fer- 
tile country  into  a  howling  wilderness.  In  an  incredibly  short 
space  of  time,  every  green  thing  on  their  line  of  march  is 
destroyed,  every  leaf  is  stripped  from  every  tree,  every  blade 
of  grass  and  corn  is  eaten  down,  and  it  is  not  until  the  ground 
is  utterly  bare  and  brown  that  the  locusts  take  wing  and  seek 
out  some  fresh  region  to  devastate. 

ORDER  VI.  NEUEOPTEEA  (Gr.  neuron,  nerve;  pteron, 
wing). — The  mouth  in  this  order  is  fitted  for  mastication;  the 
wings  are  four  in  number,  generally  nearly  equal  in  size,  all 
membranous,  and  traversed  by  numerous  delicate  nervures, 
which  interlace  so  as  to  form  a  delicate  net-work  (Fig.  68). 
The  metamorphosis  is  generally  incomplete,  but  is  sometimes 
complete. 

This  order  includes  the  well-known  and  rapacious  Dragon- 
flies  (Libellulidce),  the  Caddis-flies  (Phryganeidce),  the  May- 
flies (Ephemeridce),  the  Ant-lion  (Myrmeleo),  the  Aphis-lion 
(Fig.  68),  Termites,  etc.  The  last  of  these — namely,  the  Ter- 
mites or  white  ants — are  social  insects,  living  in  organized 
communities,  and  exhibiting  many  remarkable  phenomena. 
They  are  mostly  inhabitants  of  hot  countries,  and  cause  im- 
mense mischief  by  destroying  wood-work  of  all  descriptions. 


ORDERS   OF  INSECTS. 


157 


Though  called  "  white  ants,"  it  is  to  be  remembered  that  they 
are  not  related  in  any  way  to  the  true  ants.  They  build 
mounds  of  different  shapes  and  sizes,  sometimes  several  feet 
in  height,  formed  of  "  particles 
of  earth  worked  into  a  mate- 
rial as  hard  as  stone."  Each 
family  of  Termites  (Fig.  69) 
possesses  a  king  and  queen, 
which  are  always  kept  together 
closely  guarded  in  a  chamber 
placed  in  the  centre  of  the 
nest.  The  king  (Fig.  69,  a) 
and  the  queen  (b)  both  origi- 
nally possessed  wings,  but  they 
lose  these  as  soon  as  they 
found  a  colony.  Both  are  much 
larger  than  the  bulk  of  the 
community,  the  queen  im- 
mensely SO,  Owing  to  the  FIG.  68.— Neuroptera.  Aphis-lion  (Hemero- 

enormous  distention  of  her  ab-  m^  *****  **"> and  e^8' 

domen  with  eggs.  The  ordinary  Termites  are  all  sterile  fe- 
males, incapable  of  laying  eggs,  and  they  are  divided  into  two 
;i;t.4-;nA+  OQfo  ™.  "castes,"  both  destitute  of  wings,  and  differ- 


distinct  sets  or 


ing1  in  the  armature  of  the  head.     The  one  caste  includes  the 


FIG.  69.— Termites  (Termes  bellicovus);  a  King,  before  the  wings  are  cast  off;  Z>  Queen, 
with  the  abdomen  distended  with  eggs ;  c  Worker ;  d  Soldier. 

so-called  "  workers,"  who  perform  all  the  ordinary  work  of  the 
colony,  while  the  "  soldiers  "  have  greatly-developed  jaws,  and 
are  simply  occupied  in  defending  the  nest  against  all  enemies. 

8 


158 


INVERTEBRATE  ANIMALS. 


SECTION  III.  HOLOMETABOLA. — Metamorphosis  complete  ; 
the  larva,  pupa,  and  imago,  differing  greatly  from  one  an- 
other in  external  appearance.  The  larva  worm-like,  and  the 
pupa  quiescent. 

ORDER  VII.  APHANTPTERA  (Gr.  aphanos,  inconspicuous ; 
pteron,  wing). — In  this  order  are  only  the  Fleas  (Pulicidce),  in 
which  the  mouth  is  suctorial,  the  metamorphosis  is  complete, 
and  the  wings  are  rudimentary,  being  represented  by  four 
minute  scales  placed  on  the  last  two  segments  of  the  thorax. 
The  larva  of  the  common  flea  is  a  footless  grub,  which  in 
about  twelve  days  spins  a  cocoon  for  itself,  and  becomes  a 
quiescent  pupa,  from  which  the  imago  emerges  in  about  a 
fortnight  more. 

ORDER  VIII.  DIPTERA  (Gr.  dis,  twice ;  pteron,  wing). — 
The  insects  of  this  order,  as  implied  by  its  name,  have  only  a 
single  pair  of  wings — namely,  the  anterior  pair.  The  poste- 
rior wings  are  rudimentary,  and  are  represented  by  two 


FIG.  70.— Diptera.    Crane-fly  (Tipula  oleracea). 

clubbed  filaments  called  "  balancers  "  or  "  poisers  "  (Fig.  70). 
The  mouth  in  the  Diptera  is  suctorial. 


ORDERS   OF  INSECTS. 


159 


The  Diptera  constitute  one  of  the  largest  orders  of  insects ; 
the  House-flies  and  Flesh-flies  (Musca),  the  Gnats  ( Cltleoo),  the 
Crane-flies  (Tipula),  the  Forest-flies  (Hippobosca),  and  the 
Gad-flies  (Tabanidce),  constituting  good  examples. 

ORDER  IX.  LEPIDOPTERA  (Gr.  lepis,  scale ;  pferon,  wing). 
— This  well-known  and  most  beautiful  of  all  the  orders  of  in- 
sects comprises  the  Butterflies  and  Moths,  the  former  being 
active  by  day  (diurnal),  and  the  latter  mostly  toward  twilight 
(crepuscular),  or  at  night  (nocturnal).  In  all  the  Lepidoptera 
the  mouth  of  the  adult  insect  is  purely  suctorial,  and  is  pro- 
vided with  a  spiral  trunk  fitted  for  imbibing  the  juices  of 
flowers.  The  wings  are  four  in  number,  and  are  covered  more 
or  less  completely  with  modified  hairs  or  scales,  which  are 
pretty  objects  under  the  microscope,  and  from  which  the  wings 
derive  their  beautiful  colors.  The  larvae  of  the  Lepidoptera 
(Fig.  71)  are  generally  known  as  caterpillars.  They  are  worm- 
like,  provided  with  masticatory  organs  fitted  for  dividing  solid 


FIG.  71.— Large  white  Cabbage-butterfly  (Pontia  brasvicce).    a  Larva  or  caterpillar;   & 
Pupa  or  chrysalis;  c  Imago  or  perfect  insect. 

substances,  possessing  false  legs  in  addition  to  the  three  pairs 
proper  to  the  adult,  and  having  attached  to  the  under  lip  a 
tubular  organ  or  spinneret,  by  which  silken  threads  can  be 
manufactured. 

The  butterflies  or  diurnal  Lepidoptera  are  characterized  by 
being  active  during  the  daytime,  by  keeping  their  wings  most- 


160  INVERTEBRATE  ANIMALS. 

ly  erect  when  at  rest  (Fig.  71,  c),  by  having  club-shaped  an- 
tennae, and  by  having  a  chrysalis  (#),  which  is  almost  always 
naked  and  angular,  and  is  generally  attached  to  some  solid 
object  by  silken  threads  variously  disposed. 

The  Moths  are  mostly  active  during  the  night-time,  when 
they  are  said  to  be  nocturnal.  Many  of  them,  however,  are 
"  crepuscular  " — that  is  to  say,  they  are  active  during  the  hours 
of  twilight ;  and  a  few  come  out  in  broad  daylight  and  in  the 
brightest  sunshine.  The  pupaa,  or  chrysalides,  are  never  an- 
gular, as  in  the  case  of  the  butterflies. 

Apart  from  the  destruction  committed  by  the  Caterpillars 
of  some  of  the  Lepidoptera,  the  only  members  of  the  order 
which  are  of  importance  to  man  are  the  various  species  of 
Bombyx,  from  which  silk  is  derived.  Several  species  are  cul- 
tivated for  this  purpose,  but  by  far  the  most  valuable  is  the 
common  Silk-moth  (Bombyx  Mori\  which  owes  its  name  to 
the  fact  that  the  larva  feeds  upon  the  leaves  of  the  common 
Mulberry  (Morus  nigra).  It  is  hardly  necessary  to  say  that 
raw  silk  is  derived  from  the  "  cocoon,"  or  silken  case  in  which 
the  caterpillar  enwraps  itself  before  becoming  a  chrysalis. 
Most  of  the  raw  silk  is  derived  from  France,  Italy,  China,  and 
the  East  Indies. 

ORDER  X.  HYMENOPTERA  (Gr.  humen,  membrane ;  pteron, 
wing). — In  this  order  all  the  four  wings  are  present,  as  a  rule, 
and  they  are  all  membranous  in  texture,  with  few  nervures 
(Fig.  72).  The  mouth  is  always  furnished  with  biting-jaws  or 
mandibles,  but  often  is  adapted  for  suction  as  well.  The  fe- 
males have  the  extremity  of  the  abdomen  furnished  with  an 
instrument  connected  with  the  process  of  laying  eggs  (ovi- 
positor) ;  and  in  very  many  cases  this  becomes  the  powerful 
defensive  weapon  known  as  the  sting.  The  metamorphosis  is 
complete. 

The  Hymenoptera  form  a  very  extensive  order,  comprising 
the  Bees  (ApidcB),  the  Wasps  ( Vespidce),  the  Ants  (Formi- 
cidce),  the  Saw-flies  (Tenthredimdce,  Fig.  72),  and  the  Ich- 
neumons. The  Bees  and  Wasps  are  well  known  as  forming 
social  communities,  though  solitary  members  of  both  are  not 
uncommon.  In  both  groups  these  organized  communities  con- 
sist of  a  vast  number  of  undeveloped  females,  or  "  neuters  " — 
the  so-called  "  workers  " — presided  over  by  a  single  fertile  fe- 
male, or  "  queen,"  or  containing  several  such.  The  males  are 
only  produced  at  certain  seasons,  and  they  constitute  the  so- 
called  "  drones  "  of  a  hive  of  bees.  The  workers  discharge  all 


ORDERS   OF  INSECTS. 


161 


the  duties  necessary  for  the  preservation  of  the  colony,  such 
as  procuring  food,  building  the  nest,  and  feeding  the  young. 
As  there  is  only  one  set,  or  "  caste,"  of  neuters,  the  duty  of 


FIG.  72. — Gooseberry  Saw-fly  (Tenthredo  grossulari<%\  larva,  pupa,  and  imago.         1 

defending  the  nest  falls  to  the  lot  of  all  the  workers,  and  is 
not  delegated  to  a  special  class  of  soldiers.  The  queen  is  the 
founder  of  the  colony,  and  her  sole  function,  after  starting  the 
community,  is  to  lay  eggs.  The  drones,  or  .males,  do  no  work, 
as  a  rule,  and  they  either  die,  or  are  killed  by  the  workers,  as 
soon  as  the  female  is  fertilized. 

The  Ants  likewise  form  communities,  consisting  of  males, 
females,  and  neuters.  The  males  and  females,  like  those  of 
the  very  different  "White  Ants,"  or  Termites,  are  winged 
(Fig.  73,  a),  and  are  produced  in  great  numbers  at  particular 
times  of  the  year.  They  then  quit  the  nest  and  pair,  after 
which  the  fecundated  females  lose  their  wings  and  form  fresh 
societies.  The  workers  (Fig.  73,  b)  are  sometimes  all  of  one 
kind,  but  they  are  often  divided  into  two,  or  even  three, 
distinct  classes  or  "castes."  The  Ants  exhibit  many  most 
extraordinary  and  interesting  instincts  and  habits,  of  which 


162  INVERTEBRATE  ANIMALS. 


FIG.  73.— The  Bed  Ant  (Myrmica  rvfa).    a  Winged  male;  6  "Wingless  female.    Magnified. 

their  custom  of  "milking"  the  little  Plant-lice  has  been  al- 
ready mentioned.  Another  very  singular  habit  of  some  Ants 
may  be  just  alluded  to — their  habit,  namely,  of  capturing  the 
pupae  of  other  species  of  Ants  and  bringing  them  up  as  slaves. 
The  relations,  however,  between  the  masters  and  slaves  vary 
a  good  deal  in  different  cases.  In  the  case,  for  instance,  of 
the  Russet  Ant  (Formica  rufescens)  the  masters  are  so  entire- 
ly dependent  upon  their  slaves  that  they  cannot  even  feed 
themselves,  and  the  only  work  which  they  perform  unassisted 
is  the  capturing  of  fresh  slaves.  In  the  Blood-red  Ant  (For- 
mica sanguined) ,  on  the  other  hand,  the  slaves  are  much 
fewer  in  number,  and  the  masters  are  much  less  dependent 
upon  their  good  offices.  In  all  cases,  the  slaves  exhibit  the 
greatest  devotion  to  their  masters,  and  are  invariably  taken 
the  greatest  care  of  by  their  captors. 

ORDER  XL  STREPSIPTERA  (Gr.  strepho,  1  twist ;  pteron, 
wing). — This  is  an  extremely  small  order  of  insects,  which 
merely  requires  to  be  mentioned.  It  includes  only  certain 
minute  parasites,  which  are  found  on  bees  and  other  Ily- 
menoptera.  The  females  are  destitute  of  wings  or  feet,  and 
are  merely  soft,  worm-like  grubs.  The  males  are  active,  and 
possess  a  single  pair  of  large  membranous  wings.  Unlike  the 
Diptera,  it  is  the  posterior  pair  of  wings  which  is  present,  and 
the  anterior  pair  is  quite  rudimentary,  and  is  only  represented 
by  curious  twisted  filaments,  from  which  the  name  of  the 
order  is  derived. 

ORDER  XII.  COLEOPTERA  (Gr.  Jcoleos,  a  sheath ;  pteron, 
wing). — The  twelfth  and  last  order  of  insects  is  that  of  the 
Coleoptera,  including  the  well-known  insects  familiar  to  every 


ORDERS  OF  INSECTS.  163 

one  under  the  name  of  "  beetles."  The  leading  peculiarity  of 
the  Coleoptera  is  to  be  found  in  the  fact,  that  though  all  the 
four  wings  are  present,  only  the  posterior  pair  are  mem- 
branous, and  perform  the  function  of  wings.  The  anterior  pair 
of  wings  are  no  longer  capable  of  being  used  in  flight,  but  are 
hardened  by  the  deposition  of  chitine,  and  constitute  pro- 


FIG.  74.— Coleoptera.     The  common  Cockchafer  (Melolontha  vulgaris),  with  the  elytra 
closed,  and  in  flight. 

tective  cases,  which  cover  the  hind-wings,  and  are  known  as 
"  elytra  "  (Gr.  elutron,  a  sheath).  The  mouth  in  all  the  beetles 
is  masticatory,  and  is  furnished  with  biting  and  chewing  jaws. 

The  larvae  of  the  beetles  are  all  worm-like  grubs,  with 
masticatory  mouths,  and  they  all  pass  through  a  complete  meta- 
morphosis, generally  requiring  a  protracted  period  for  its  com- 
pletion. The  known  number  of  different  kinds  of  beetles  can- 
not be  estimated  with  any  certainty,  but  it  is  probably  little 
short  of  50,000  species,  and  this  estimate  has  been  doubled 
by  some  writers.  They  are,  as  a  general  roile,  remarkable  for 
their  hard,  chitinous  skin,  their  glittering,  often  metallic, 
colors,  and  their  voracious  habits,  though  many  of  them  feed 
upon  vegetable  matters. 

Of  the  enormous  number  of  known  Beetles,  the  only  one 
which  can  be  said  to  be  of  any  decided  use  to  man  is  the  so- 
called  "  Blister-beetle,"  or  "  Spanish  Fly  "  ( Cantharis  vesicar 
toria).  This  handsome  insect  is  a  native  of  Southern  Europe, 
especially  of  Italy,  Spain,  and  France,  and  lives  upon  the 
leaves  of  the  ash,  lilac,  elder,  and  poplar.  It  is  largely  col- 
lected and  exported  for  medicinal  purposes,  as  it  yields  one  of 
the  most  generally  used  and  efficient  of  blisters. 


SUB-KINGDOM  V.— MOLLUSCA. 
CHAPTER   XIX. 

SUB-KINGDOM  MOLLUSCA.  —  The  Mollusca  (Lat.  mollis, 
soft),  as  implied  by  their  scientific  name,  are  mostly  soft- 
bodied  animals,  but  their  popular  name  of  "  shell-fish "  ex- 
presses the  fact  that  their  soft  body  is  usually  protected  by 
an  external  skeleton  or  "  shell."  All  the  Mollusca  are  fur- 
nished with  a  distinct  alimentary  canal,  which  is  completely 
shut  off  from  the  general  cavity  of  the  body  (Fig.  75,  a). 
There  is  sometimes  no  distinct  blood-circulatory  apparatus ;  but, 
when  there  is,  its  central  portion  (i.  e.,  the  heart)  is  placed  upon 
the  dorsal  aspect  of  the  body.  The  chief  peculiarity,  however, 


FIG.  75. — Diagram  of  a  Mollusk.    a  Alimentary  canal;  h  Heart;  /  Foot;  n  Cerebral  gan- 
glion; n'  Pedal  ganglion ;  n"  Parieto-splanchnic  ganglion. 

of  the  Mollusca  is  found  in  the  nature  of  the  nervous  system. 
In  the  lower  forms  (Fig.  76,  2  d),  the  nervous  system  consists 
essentially  of  a  single  ganglionic  mass,  giving  off  filaments  in 
various  directions.  In  the  higher  Mollusca  (Fig.  75,  n),  the 
nervous  system  consists  of  three  scattered  ganglia,  united  to 
one  another  by  nervous  cords.  One  of  these  ganglia  is  placed 
above  the  gullet  or  oesophagus,  and  is  known  as  the  "  supra- 
cesophageal  "  or  "  cerebral  "  ganglion.  A  second  supplies 


MOLLUSCA.  165 

nerves  to  the  great  locomotive  organ  of  most  Mollusks,  the 
"  foot,"  and  is  therefore  called  the  "  pedal "  ganglion.  The 
third  is  known  by  the  cumbrous  name  of  the  "  parieto-splanch- 
nic "  ganglion,  because  it  supplies  nervous  filaments  to  the 
walls  (parietes)  of  the  body,  and  also  to  the  internal  organs 
(splanchna).  In  all  the  higher  Mollusks  it  is  this  scattered 
condition  of  the  nervous  masses  which  distinguishes  them  so 
sharply  from  all  other  animals.  Distinct  respiratory  organs 
may  or  may  not  be  present,  and  they  may  be  adapted  for 
breathing  air  directly  or  through  the  medium  of  water.  All 
the  higher  Mollusca  are  simple  animals,  and  perpetuate  their 
kind  by  means  of  the  sexes,  but  many  of  the  lower  forms 
have  the  power  of  producing  colonies  by  continuous  gemma- 
tion, much  as  we  have  formerly  seen  in  the  Hydroid  Zoo- 
phytes. 

The  digestive  system  in  all  the  Mollusca  consists  of  a 
mouth,  gullet,  stomach,  intestine,  and  anus,  with  the  excep- 
tion of  a  few  forms  in  which  the  intestine  ends  blindly.  In 
some  the  month  is  surrounded  by  ciliated  tentacles  (Polyzoa, 
Fig.  77)  ;  in  others,  it  is  furnished  with  two  long  ciliated  arms 
(Brachiopoda)  ;  in  the  bivalves  (Lamellibranchiata),  it  is 
mostly  furnished  with  four  membranous  processes  or  "  palpi " 
(Fig.  80,  p)  ;  in  others,  it  is  furnished  with  a  complicated 
toothed  organ  or  "  odontophore  "  ( Gasteropoda,  Fig.  83,  and 
Pteropoda) ;  and  lastly,  the  Cephalopoda,  in  addition  to  an 
odontophore,  possess  horny  mandibles,  forming  a  kind  of  beak, 
very  like  that  of  a  parrot. 

The  blood  is  colorless,  or  nearly  so.  In  the  lowest  class  of 
the  Mollusca  (Potyzoa),t\\e  circulation  is  carried  on  by  means 
of  cilia,  and  there  is  no  distinct  heart,  nor  any  definite  course 
of  the  circulating  fluid.  In  the  Sea-squirts  (Tunicata),  there 
is  a  distinct  heart,  but  the  structure  of -this  is  very  simple, 
consisting  of  a  mere  tube,  open  at  both  ends,  so  that  the 
course  of  the  circulation  is  periodically  reversed.  In  the 
higher  Mollusca,  there  is  a  distinct  heart,  consisting  of  two 
chambers,  of  which  one  (the  auricle)  receives  the  aerated 
blood  from  the  gills,  while  the  other  (the  ventricle)  drives  it 
through  the  body. 

Respiration  is  very  variously  effected  among  the  Mollusca. 
In  the  Polyzoa  (Fig.  77)  respiration  is  discharged  mainly  by 
the  crown  of  ciliated  tentacles  surrounding  the  mouth.  In  the 
sea-squirts  (Fig.  78),  respiration  is  effected  by  a  greatly-devel- 
oped pharynx,  which  is  perforated  by  numerous  ciliated  aper- 
tures. In  the  lamp-shells  and  their  allies  (^Brachiopoda)^  the 


166  INVERTEBRATE  ANIMALS. 

long,  ciliated  arms,  which  spring  from  the  sides  of  the  mouth, 
seem  to  be  the  main  agents  in  respiration.  In  the  bivalve- 
shell-fish,  the  cuttle-fishes,  and  most  of  the  univalves,  the 
breathing-organs  are  in  the  form  of  gills  or  branchiae,  adapted 
for  breathing  air  dissolved  in  water.  In  the  remainder  of  the 
univalves  (e.  g.,  snails  and  slugs),  the  breathing-organs  are 
adapted  for  breathing  air  directly,  and  have  the  form  of  an 
air-chamber  or  pulmonary  sac,  produced  by  the  folding  of  a 
portion  of  the  mantle.  The  air  is  admitted  to  the  chamber  by 
a  round  opening,  situated  on  the  side  of  the  neck,  and  capable 
of  being  closed  at  will.  The  lining  membrane  of  the  chamber 
is  richly  supplied  with  blood-vessels,  and  thus  the  necessary 
purification  of  the  blood  is  carried  out. 

In  accordance  with  the  scattered  or  rudimentary  condition 
of  the  nervous  system,  the  Mbllusca  are  not  characterized  by 
acuteness  of  senses,  nor  by  any  great  power  of  locomotion. 
Organs  of  sight  exist  in  some  of  the  lower  and  many  of  the 
higher  Mbllusca,  attaining  in  the  cuttle-fishes  (Fig.  89)  an  ex- 
tremely high  type  of  organization.  The  common  bivalve  shell- 
fish, such  as  the  scallop,  possess  numerous  simple  eyes  placed 
along  the  margins  of  the  mantle,  but,  in  many  cases,  even  these 
are  absent.  Locomotion  is  very  variously  effected,  but  seldom 
with  much  vigor  or  activity.  The  lowest  classes  of  the  Mol- 
lusoa  are,  in  the  great  majority  of  instances,  fixed  when  adult. 
The  common  univalve  shell-fish,  such  as  whelks,  snails,  slugs, 
etc.,  creep  about  slowly  by  means  of  a  flattened  disk,  devel- 
oped on  the  under  surface  of  the  body,  and  known  as  the 
"foot."  Other  Univalves  and  many  Bivalves  can  effect  short 
leaps  by  means  of  the  foot,  but  many  of  the  latter  are  perma- 
nently fixed  to  solid  objects,  or  buried  in  the  sand.  The  mi- 
nute Mollusca,  known  as  the  Pteropoda  (Fig.  88),  swim  freely 
at  the  surface  of  the  ocean  by  means  of  two  fins,  formed  by  a 
modification  of  the  foot,  and  attached  to  the  sides  of  the  head. 
The  only  Mollusks  which  enjoy  really  active  powers  of  loco- 
motion are  the  predacious  cuttle-fishes,  which  swim  rapidly  by 
means  of  fins,  or  by  ejecting  a  jet  of  water  from  the  cavity  of 
the  mantle,  and  which  can  also  creep  about  by  means  of  the 
"  arms  "  placed  around  the  mouth  (Fig.  89). 

The  last  feature  in  the  Mollusca  which  requires  to  be  men- 
tioned is  the  "  shell."  The  shell  is  not  invariably  and  univer- 
sally present  in  the  Mollusca,  many  being  either  destitute  of 
a  shell  altogether,  or  having  one  so  small  that  it  would  not  com- 
monly be  recognized  as  such.  In  these  cases,  as  in  the  com- 
mon slugs,  the  animal  is  said  to  be  "  naked."  In  all  the  Mol- 


MOLLUSCA.  167 

lusca  which  possess  a  shell,  this  is  secreted  by  the  integument, 
or  by  what  is  technically  called  the  mantle,  and,  in  all  cases, 
it  is  composed  of  carbonate  of  lime.  The  methods  in  which 
the  lime  is  arranged  differ  in  different  cases,  but  all  living 
shells  have  an  outer  covering  of  animal  matter,  which  is 
known  as  the  "  epidermis."  In  a  great  many  of  the  higher 
Mollusca,  such  as  the  whelks,  periwinkles,  snails,  and  others, 
the  shell  consists  of  only  a  single  piece,  when  it  is  said  to  be  "  uni- 
valve." In  many  others,  such  as  oysters,  mussels,  scallops,  etc., 
the  shell  is  composed  of  two  pieces,  and  is  then  said  to  be 
"  bivalve."  In  a  few  forms,  the  shell  consists  of  several  pieces, 
and  it  is  then  said  to  be  "  multivalve."  The  more  important 
variations  in  the  shells  of  the  Mollusca  will  be  noticed  in 
speaking  of  the  different  classes  of  the  sub-kingdom. 

In  accordance  with  the  nature  of  the  nervous  system,  the 
Mollusca  are  divided  into  two  great  divisions,  known  respec- 
tively as  the  Molluscoida  and  Mollusca  proper.  In  the  Mol- 
luscoida, the  nervous  system  consists  of  a  single  ganglion,  or 
principal  pair  of  ganglia,  and  there  is  either  no  circulatory 
organ  or  an  imperfect  heart.  In  this  division  are  included  the 
three  classes  of  the  Sea-mosses  (Polyzod),  the  Sea-squirts  (Tu- 
nicata),  and  the  Lamp-shells  and  their  allies  (Brachiopoda).  In 
the  Mollusca  proper,  the  nervous  system  consists  of  three 
principal  pairs  of  ganglia,  and  there  is  a  well-developed  heart, 
consisting  of  at  least  two  chambers.  Under  this  head  come 
all  the  ordinary  forms  of  shell-fish. 


CHAPTER    XX. 

MOLLUSCOIDA. 

CLASS  I.  POLYZOA  (Gr.  polus,  many  ;  zoon,  animal.)  — 
The  members  of  this  class  are  the  lowest  of  all  Molhtsca, 
and  they  are  generally  known  by  the  popular  names  of  "  Sea- 
mosses  "  and  "  Sea-mats."  They  are  invariably  compound, 
forming  associated  growths  or  colonies,  each  consisting  of  a 
number  of  distinct  but  similar  zoftids,  produced  by  gemmation 
from  a  single  primordial  individual.  The  colonies  thus  pro- 
duced are  very  generally  protected  by  a  horny  or  chitinous 
integument,  and  they  are  so  like  the  Hydroid  Zoophytes  that 
they  were  long  described  as  such.  The  only  absolute  distinc- 
tion between  the  two  classes  is  to  be  found  in  the  internal 
structure  of  the  zoo'ids  of  each  ;  .  but  they  may  be  generally 
separated  by  the  fact  that  the  separate  cells  in  a  compound 
Hydroid  are  all  united  to  one  another  by  means  of  a  common 
flesh  or  ccenosarc ;  whereas  in  the  Polyzoa  the  separate  cells 
composing  the  colony  are  merely  connected  externally,  but 
very  rarely  have  any  direct  communication  with  each  other. 
The  separate  beings  or  zooids  which  collectively  constitute  the 
colony  of  any  Polyzoon  are  spoken  of  as  "  polypides  " — the 
term  polypite  being  only  used  in  connection  with  the  Hydro- 
zoa,  and  the  term  polype  being  similarly  restricted  to  the 
Actinozoa. 

Each  polypide  in  a  typical  Polyzoon  has  the  following 
structure  (Fig.  76,  2) :  The  body  of  the  animal  is  enclosed  in  a 
double-walled  sac,  of  which  the  outer  layer  is  usually  chitinous 
or  calcareous,  and  constitutes  a  "  cell "  in  which  the  zo5id  is 
contained.  This  outer  layer  is  known  as  the  "  ectocyst,"  to 
distinguish  it  from  the  ectoderm  of  the  Ccelenterata.  The 
cell,  thus  formed,  is  lined  by  a  much  more  delicate  membra- 
nous layer,  which  is  known  as  the  "  endocyst."  This  membra- 


MOLLTJSCOIDA. 


109 


nous  sac,  formed  by  the  endocyst,  is  pierced  by  two  openings. 
One  of  these  is  the  mouth,  and  it  is  always  surrounded  by  a 
circle  or  crescent  of  hollow  ciliated  processes  or  tentacles 
(Fig.  76,  2,  a).  These  ciliated  tentacles  serve  partly  as  respi- 
ratory organs,  and  partly  to  set  up  a  current  of  water  by 
which  floating  particles  of  food  are  brought  to  the  mouth. 
The  mouth  and  tentacular  crown  can  be  partially  or  com- 
pletely pulled  into  the  sac  by  means  of  a  muscle  which  is  fixed 
to  the  gullet  (2,  g).  The  mouth  leads  into  a  gullet,  and  that 


FIG.  76. — Morphology  of  Polyzoa.  1.  Fragment  of  one  of  the  Sea-mats  (Flustra  truncata\ 
magnified  to  show  the  cefls.  2.  Diagram  of  a  single  polypide  of  a  PolyzoOn  (after  Allman) : 
a  Mouth  surrounded  by  the  ciliated  tentacles ;  6  Alimentary  canal ;  c  Anus ;  d  Nervoua 
ganglion;  e  Investing  sac  or  "  ectocyst ;"  ff  ^Reproductive  organs ;  g  Muscle.  3.  BirdV 
head  process. 

again  into  a  stomach,  sometimes  with  a  muscular  gizzard  be- 
tween. From  the  stomach  proceeds  an  intestine  of  variable 
length,  which  terminates  by  a  distinct  anus  at  the  upper  part 
of  the  sac  (2,  c).  On  one  side  of  the  gullet,  between  it  and 
the  anus,  is  placed  a  single  nervous  ganglion  (d).  Distinct 
reproductive  organs  (ff)  are  also  present,  and  the  whole  cav- 
ity of  the  sac  is  filled  with  fluid.  From  the  above  description 
it  will  be  evident  that  the  typical  polypide  of  a  Polyzoon 
differs  from  the  polypite  of  a  Hydrozoon  in  having  a  distinct 
alimentary  canal  suspended  freely  in  a  body-cavity,  and  hav- 
ing both  a  mouth  and  vent,  in  having  a  distinct  nervous  sys- 
tem, and  in  having  the  reproductive  organs  contained  within 


INVERTEBRATE  ANIMALS. 


the  body.  On  the  other  hand,  in  the  Hydrozoa,  there  is  no 
alimentary  canal  distinct  from  the  body-cavity,  there  is  no 
nervous  system,  and  the  reproductive  organs  are  in  the  form 
of  external  processes  of  the  body-wall. 


FIG.  77. — 1.  Fragment  of  F lustra  truncata,  one  of  the  Sea-mats,  natural  size.  2.  A  single 
polypide  of  Valkeria,  magnified,  showing  the  circular  crown  of  tentacles.  3.  A  polypide 
of  Loplwpus  crystalUnufi,  &  fresh-water  Polyzoon,  highly  magnified,  showing  the  horse- 
shoe shaped  crown  of  tentacles :  a  Tentacular  crown ;  &  Gullet;  c  Stomach;  S  Intestine; 
eAnus;  g  Gizzard;  k  Endocyst;  I  Ectocyst. 

The  foregoing  gives  the  essential  structure  of  the  polypide 
of  any  Polyzoon^  but  in  nature  this  simplicity  is  lost.  In  all 
cases  in  nature  the  primitive  polypide  possesses  the  power  of 
producing  fresh  zo5ids  by  a  process  of  budding;  and  these 
zooids  remain  attached  to  one  another,  so  that  ultimately  there 
is  produced  a  compound  growth  or  colony.  Further,  in  almost 
all  the  Polyzoa^  the  outer  layer  of  the  polypide  is  more  or  less 
hardened  by  the  deposition  in  it  of  chitine  or  of  carbonate  of 
lime.  The  skeletons  thus  formed  are  the  parts  of  the  colony 
which  are  most  familiarly  known,  and  in  the  case  of  the  com- 
mon Sea-mats  (Fig.  77,  1)  they  are  very  well  known  to  sea- 
side visitors,  and  are  generally  regarded  as  sea-weeds.  Exam- 
ined in  its  dead  state,  such  a  skeleton  only  shows  a  number 
of  little  horny  chambers  or  cells  (Fig.  76,  1),  each  with  a  little 
aperture.  When  alive,  however,  each  of  these  cells  was  ten- 
anted by  a  single  zooid  or  polypide,  capable  of  protruding  its 


MOLLUSCOIDA.  171 

ciliated  head  from  the  aperture,  and  of  again  retiring  within 
it,  if  alarmed.  The  skeleton  is,  in  some  cases,  furnished  with 
curious  organs,  which  are  known  as  "  bird's-head  processes  " 
(Fig.  76,  3),  from  their  resemblance  to  the  beak  of  a  bird. 
The  parts  of  this  beak  keep  constantly  snapping  together, 
very  much  like  the  little  pincer-like  organs  called  "  pedicella- 
rias  "  in  the  sea-urchins  and  star-fishes ;  but  it  is  difficult  to  see 
what  service  they  perform.  They  continue  their  movements 
long  after  the  death  of  the  polypides,  and  this  appears,  in  some 
cases,  at  any  rate,  to  be  due  to  a  peculiar  system  of  nerves 
known  as  the  "  colonial "  nervous  system.  In  addition,  namely, 
to  the  single  ganglion  with  which  each  polypide  is  furnished,  it 
has  been  shown  that  in  many  forms  the  zoftids  composing  the 
colony  are  united  together  by  a  well-developed  nervous  system, 
and  are  thus  brought  into  organic  connection  with  one  another. 

The  vast  majority  of  the  Polyzoa  are  fixed,  and  thus  as- 
sume a  very  plant-like  appearance.  There  is  one  fresh-water 
species,  however  (viz.,  Cristatella),  in  which  the  colony  can 
creep  about  upon  a  flattened  base  very  like  the  foot  of  a  slug. 
In  this  same  form,  also,  alone  of  all  the  Polyzoa,  there  is  not 
any  outer  covering  or  ectocyst  to  the  polypides. 

The  Polyzoa  are  partly  inhabitants  of  the  sea  and  partly 
of  fresh  water,  and  they  are  thus  divided  into  two  groups 
which  differ  from  one  another  very  much  in  anatomical  struc- 
ture. In  most  of  the  fresh-water  Polyzoa  the  tentacles  are 
borne  upon  a  crescentic  disk  or  stage  (Fig.  77,  3),  so  that  the 
crown  of  tentacles  assumes  the  shape  of  a  horseshoe.  In 
almost  all  the  marine  forms,  on  the  other  hand,  the  tentacles 
(Fig.  77,  2)  are  simply  arranged  in  a  circle. 

All  the  Polyzoa  are  hermaphrodite,  each  polypide  being 
furnished  with  the  reproductive  organs  proper  to  the  two 
sexes.  The  eggs  are  simply  liberated  into  the  body-cavity, 
where  they  are  fertilized ;  but  it  is  uncertain  how  the  fertilized 
ova  escape  into  the  external  medium.  Besides  true  sexual 
reproduction,  and  besides  the  power  of  producing  colonies  by 
continuous  budding,  fresh  individuals  can  be  produced  in  many 
cases  by  a  process  of  discontinuous  gemmation. 

CLASS  II.  TUNIC  ATA  (Lat.  tunica,  a  cloak). — The  mem- 
bers of  this  class  are  not  uncommonly  called  Ascidian  Mol- 
lusks  (Gr.  askos,  a  wine-skin)  from  the  resemblance  which 
many  of  them  exhibit  in  shape  to  a  two-necked  leather  bottle 
(Fig.  78,  2).  They  are  popularly  known  as  "Sea-squirts," 
from  their  power  of  .forcibly  ejecting  water  from  the  orifices 


172 


INVERTEBRATE  ANIMALS. 


of  the  bottle.  Their  scientific  name,  again,  of  Tunicata,  is 
derived  from  the  fact  that  the  body  is  enveloped  in  a  leathery 
elastic  integument,  which  consists  of  different  layers,  and  which 
takes  the  place  of  a  shell.  The  outer  covering  of  the  animal 
is  of  a  gristly  or  leathery  consistence,  and  is  known  as  the 
"  test."  It  is  remarkable  for  containing  a  considerable  propor- 
tion of  a  substance  apparently  identical  with  cellulose,  which 
is  one  of  the  most  characteristic  of  all  vegetable  products. 
The  test  is  lined  by  a  second  coat,  which  is  highly  muscular, 
and  confers  upon  the  animal  its  power  of  contracting  itself 
and  squirting  out  water.  Of  the  two  necks  which  are  placed 
at  the  anterior  end  of  a  simple  Ascidian  (Fig.  78),  one  is  per- 


x</ 


FIG.  78. — Morphology  of  Tunicata.    1.  Diagram  of  a  Tunicary  (after  Allman):  a  Oral  aper- 

res;  d  Ali- 
A  simple 


ture;  b  Atrial  aperture;  c  Respiratory  sac,  with  its  rows  of  ciliated  apertures;  d  Ali- 
mentary canal;    e  Anus;  /  Cloaca  or  atrium;   g  Nervous   ganglion. 


Ascidian  (6 


fo rated  by  the  aperture  of  the  mouth,  while  the  other  serves 
as  an  excretory  aperture.  These  two  apertures  are  known 
respectively  as  the  "  oral "  and  "  atrial "  apertures. 

The  oral  aperture  (a)  is  usually  furnished  with  a  circle  of 
small  non-retractile  tentacles,  and  opens  into  a  great  chamber 
known  by  various  names,  but  best  as  the  "  respiratory  sac." 
This  sac  occupies  the  greater  part  of  the  cavity  of  the  body 
(Fig.  78,  1,  c),  and  has  its  walls  perforated  by  numerous  aper- 
tures, the  sides  of  which  are  ciliated.  At  the  bottom  of  the 
respiratory  sac  is  a  second  opening  (the  mouth  of  some 


MOLLUSCOIDA.  173 

writers)  which  leads  by  a  short  gullet  into  a  capacious  stom- 
ach (d).  From  the  stomach  an  intestine  is  continued  to  ter- 
minate by  a  distinct  anus,  which  does  not  communicate  direct- 
ly with  the  exterior,  but  opens  into  a  second  great  chamber, 
known  as  the  "cloaca"  or  "atrium"  (e).  The  cloaca,  in  turn, 
opens  on  the  exterior  by  the  second,  or  atrial  aperture,  in  the 
test  (b).  These  two  great  chambers — namely,  the  respiratory 
sac  and  the  cloaca — occupy  the  greater  part  of  the  body-cavity, 
and,  where  their  walls  come  into  contact,  a  free  communication 
is  established  between  the  two  by  means  of  the  ciliated  aper- 
tures already  spoken  of  as  perforating  the  respiratory  sac. 
The  cilia  which  fringe  these  apertures  all  work  toward  the 
cloaca,  and  thus  a  constant  current  of  water  is  caused  to  set 
in  by  the  oral  aperture,  through  the  respiratory  sac,  into  the 
cloaca,  and  out  again  by  the  atrial  aperture.  In  this  way 
respiration  is  effected,  the  walls  of  the  respiratory  sac  being 
almost  made  up  of  blood-vessels.  A  distinct  heart  is  present 
in  all  the  Tunicata,  but  it  has  a  very  simple  structure  (1,  h). 
It  consists  of  a  simple  tube,  open  at  both  ends,  and  not  pro- 
vided with  valves.  In  consequence  of  this,  the  circulation  in 
the  majority  of  Tunicaries  is  periodically  reversed,  the  blood 
being  driven  for  a  certain  number  of  contractions  in  one  direc- 
tion, and  then  propelled  for  a  like  period  in  an  opposite  direc- 
tion; so  that  "the  two  ends  of  the  heart  are  alternately 
arterial  and  venous." 

The  nervous  system  in  the  Tunicata  consists  of  a  single 
ganglion  placed  on  one  side  of  the  oral  aperture. 

With  one  or  two  exceptions  all  the  Tunicata  are  hermaph- 
rodite, the  organs  of  reproduction  being  situated  in  a  fold 
of  the  intestine,  and  opening  into  the  cloaca.  The  embryo  is 
at  first  free,  and  in  most  swims  about  by  means  of  a  long  tail, 
so  that  it  presents  considerable  resemblance  to  the  tadpole  of 
a  frog. 

The  Tunicata  are  all  marine,  but  differ  a  good  deal  from 
one  another  in  form.  In  the  so-called  "  simple  "  Ascidians  the 
animal  has  the  shape  figured  above,  and  is  fixed  to  some  solid 
object  by  one  end  of  the  test.  In  the  "  social "  Ascidians  the 
organism  consists  of  a  number  of  zooids,  produced  by  con- 
tinuous budding,  and  connected  together  by  a  common  tube, 
through  which  the  blood  circulates.  In  the  so-called  "  com- 
pound" Ascidians  the  tests  are  fused  together  into  a  com- 
mon gelatinous  mass,  in  which  the  individuals  are  imbedded 
in  groups.  Some  of  the  Tunicata  are  oceanic  —  that  is  to 
say,  are  found  floating,  or  swimming,  at  the  surface  of  the 


174  INVERTEBRATE  ANIMALS. 

open  ocean — and  some  exhibit  the  phenomenon  of  phospho- 
rescence. 

In  the  foregoing  description  it  has  been  found  impossible  to  convey  even 
the  most  elementary  outline  of  the  anatomy  of  a  Tunicate  without  having 
recourse  to  technical  terms.  There  still  remain  a  few  points  of  homology 
which  should  be  mentioned.  In  the  foregoing,  the  so-called  "oral  aperture" 
of  the  animal  has  been  regarded  as  truly  the  mouth,  this  being  the  simplest 
view,  and  the  one  held  by  Prof.  Huxley.  Upon  this  view  the  "  respiratory 
sac,"  into  which  the  mouth  opens,  must  be  regarded  as  a  greatly-developed 
pharynx  (i.  e.,  the  upper  portion  of  the  alimentary  tube).  Similarly,  on  this 
view,  the  lower  aperture  of  the  respiratory  sac  will  have  to  be  regarded  as 
the  opening  of  the  gullet.  By  Prof.  Allman,  again,  the  respiratory  sac  is 
looked  upon  as  formed  by  a  great  modification  of  organs  corresponding  to 
the  ciliated  tentacles  of  the  Polyzoa,  so  that  the  lower  aperture  of  the  respira- 
tory sac  is  the  true  mouth.  Lastly,  by  Prof.  Rolleston  the  respiratory  sac  is 
looked  upon  as  corresponding  to  the  gills  of  the  Bivalve  shell-fish  (Lamelli- 
branchiatd),  and  the  oral  and  atrial  apertures  are  regarded  as  corresponding 
to  the  "  respiratory  siphons "  of  these  same  animals.  On  this  view,  the 
lower  aperture  of  the  respiratory  sac  is  again  looked  upon  as  the  true  mouth. 
The  question  cannot  be  regarded  as  settled,  and  Huxley's  view  has  been 
here  adopted  merely  as  being  the  most  readily  intelligible  to  learners. 

CLASS  III.  BEACHIOPODA. — The  members  of  this  class  are 
little  known  to  the  general  public,  being  all  marine,  often  in- 
habiting considerable  depths  in  the  sea,  and  being  much  more 
abundantly  represented  by  fossil  forms  than  by  living  ex- 
amples. They  are  often  placed  with  the  ordinary  Bivalve  shell- 
fish (Lamellibranchiata],  in  consequence  of  their  universally 
possessing  a  shell  composed  of  two  pieces  or  valves  (Fig.  79), 
but  they  are  really  of  a  much  lower  organization.  In  their 
essential  structure  they  show  many  points  of  affinity  to  the 
Polyzoa,  but  they  are  always  simple  animals,  never  forming 
colonies,  and  they  always  have  a  bivalve  shell.  The  two  pieces 
of  which  the  shell  is  composed  are  always  placed  one  in  front 
and  one  behind,  so  that  they  are  "ventral"  and  "dorsal,"  and 
not  "right"  and  "left"  as  in  the  true  Bivalves.  The  two 
valves  of  the  shell  are  also  always  slightly,  and  sometimes 
greatly,  different  to  one  another  in  size,  so  that  the  shell  is 
said  to  be  "  inequi valve."  The  ventral  valve  is  usually  the 
largest,  and  often  possesses  a  prominent  curved  beak,  which 
is  generally  perforated  by  an  aperture  through  which  there 
passes  a  muscular  stalk  by  means  of  which  the  shell  is  at- 
tached to  some  solid  object.  In  some  cases,  however,  as  in 
Lingula  (Fig.  79),  the  stalk  of  attachment  simply  passes  be- 
tween the  valves,  and  is  not  transmitted  through  a  distinct 
aperture.  In  other  cases  the  shell  is  simply  attached  by  the 
substance  of  the  ventral  valve. 


MOLLUSCOIDA.  175 

The  inner  surface  of  the  valves  of  the 
shell  is  lined  by  expansions  of  the  integu- 
ment, which  are  called  the  "mantle-lobes," 
and  which  secrete  the  shell.  The  digestive 
organs  and  muscles  occupy  a  small  space  near 
the  apex  or  "beak"  of  the  shell,  which  is 
partitioned  off  by  a  membranous  partition, 
perforated  by  the  aperture  of  the  mouth.  The 
remainder  of  the  cavity  of  the  shell  is  almost 
filled  by  two  long  processes,  derived  from  the 
sides  of  the  mouth,  fringed  with  lateral 
branches,  and  termed  the  "arms."  y  These 
arms  are  usually  closely  coiled  up,  and  serve 
to  obtain  food  for  the  animal.  It  is  from  these 
organs  that  the  name  of  the  class  is  derived 
(Gr.  bracMon,  arm;  and  podes,  feet).  The 
arms  also  serve  as  respiratory  organs,  and  in 
many  forms  they  are  supported  on  an  internal 
calcareous  framework  or  skeleton,  sometimes 
called  the  "  carriage-spring  apparatus." 

The  mouth  is  placed  between  the  bases 
of  the  arms,  and  is  not  furnished  with  any 
apparatus  of  teeth.     It  conducts  by  a  gullet 
into  a  distinct  stomach,  surrounded  by  a  well-  FlGarJL"a, 
developed  granular  liver.     The  intestine  mav      the  muscular  stalk 

j.    i_      r        •   i      i       -xi          T  j.-  by  which  the  shell 

or  may  not  be  furnished  with  a  distinct  anus,      is  attached. 
but  in  no  case  does  it  open  into  the  body- 
cavity.    Within  the  lobes  of  the  mantle,  there  is  a  remarkable 
system  of  branched  tubes,  which  commence  by  blind  extremi- 
ties, and  finally  communicate  with  the  mantle-cavity  by  means 
of  certain  organs,  which  were  formerly  believed  to  be  hearts, 
and  are  now  known  as  "  pseudo-hearts."   This  system  of  tubes 
appears  to  be  mainly,  if  not  entirely,  connected  with  repro- 
duction.    A  true  heart,  however,  is  present  in  most,  if  not  in 
all,  of  the  JBrachiopoda. 

The  nervous  system  consists  of  a  single  principal  ganglion, 
connected  in  some  cases  with  others  so  as  to  form  a  collar 
round  the  commencement  of  the  gullet.  In  some  cases,  how- 
ever, the  nervous  system  appears  to  be  very  rudimentary. 

The  sexes  appear  to  be  sometimes  distinct  and  sometimes 
united  in  the  same  individual.  The  embryo,  in  some  cases,  at 
any  rate,  is  locomotive,  moving  from  place  to  place  by  means 
of  the  ciliated  arms  or  by  ventral  spines. 


CHAPTER  XXL 

MOLLFSCA     PEOPEB. 

THE  higher  Mbllusca  or  Mollusca  proper  comprise  those 
members  of  the  sub-kingdom  in  which  the  nervous  system 
consists  of  three  principal  pairs  of  ganglia  /  and  there  is 
always  a  well-developed  heart,  consisting  of  at  least  two 
chambers. 

In  this  division  are  included  the  following  classes  : 

1.  Lamellibranchiata,  without  a  distinct  head. 

2.  Gasteropoda,  )  with  ft  distinct  head  and  a  masticatory 


CLASS  I.  LAjviELLiBKAisrcHiATA.  —  These  are  well  known  as 
bivalve  shell-fish,  such  as  mussels,  oysters,  scallops,  etc.,  and 
they  are  all  either  marine  or  inhabitants  of  fresh  water.  They 
are  distinguished  from  the  other  Mollusks  by  having  no  dis- 
tinct head,  and  by  having  the  body  more  or  less  completely 
protected  by  a  bivalve-shell  composed  of  two  pieces.  They 
are  called  Lamellibranchiata  (Lat.  lamella,  a  plate  ;  Gr.  brag- 
chia,  gill),  from  the  fact  that  the  organs  of  respiration  are  in 
the  form  of  leaf-like  gills  or  branchiae,  two  of  which  are  placed 
at  each  side  of  the  body,  constituting  what  is  known  in  the 
oyster  as  the  "  beard."  The  body  of  the  Lamellibranchiata 
is  more  or  less  completely  enclosed  in  an  expansion  of  the 
integument  which  constitutes  the  "mantle,"  and  which  is 
divided  into  two  halves  or  "  lobes,"  which  are  placed  on  the 
sides  of  the  animal,  and  secrete  the  shell.  The  shell,  there- 
fore, of  the  true  bivalves  is  composed  of  two  valves,  which 
are  "  right  "  and  "  left,"  and  not  "dorsal"  and  "ventral,"  as 
in  the  Brachiopoda.  Moreover,  the  valves  of  the  shell  are 
usually  of  the  same  size,  so  that  the  shell  is  "  equivalve,"  and,, 


MOLLUSCA  PEOPER. 


177 


lastly,  the  shell  is  more  developed  on  one  side  than  the  other, 
so  as  to  become  "inequilateral"  (Fig.  81,  2).  The  lobes  of 
the  mantle  are  sometimes 
quite  free  ;  but,  at  other  times, 
they  are  more  or  less  united 
to  each  other,  and  leave  only 
two  openings.  Through  one 
of  these  openings  (the  ante- 
rior) the  "  foot "  is  protruded 
(Fig.  80,  /);  and  through 
the  other  pass  the  respiratory 
tubes  or  "  siphons  "  (s).  The 
foot  in  the  bivalves  is  a  mus- 
cular organ  developed  upon 
the  lower  surface  of  the  body, 
but  not  forming  a  creeping 
flattened  disk,  as  in  the  ordi- 
nary univalves.  In  many 
cases,  it  is  quite  rudimentary ; 
and  even  when  it  is  employed 
in  locomotion  it  is  usually 
small.  Most  generally,  it  is 
hatchet-shaped  or  pointed 
(Fig.  80,  /),  and  serves  to 
enable  the  animal  to  make 
short  leaps.  In  many  cases, 
as  in  the  common  mussels, 
the  foot  is  subsidiary  to  a 
special  gland,  which  secretes 
a  viscous  fluid,  which  hardens 
rapidly  on  exposure  to  the 
air.  This  fluid  is  moulded 
by  the  foot  into  silky  threads 
(the  so-called  "byssus"),  by 
means  of  which  the  shell  is 
firmly  fixed  to  some  solid 
object.  Besides  the  muscular 
foot,  other  muscles  are  pres- 
ent as  well  in  the  Lamelli- 
branchiata.  Of  these,  the 
most  important  are  the 
muscles  which  close  the  shell, 
and  are  called  the  "  adduc- 
tor "  muscles.  In  one  group  of  the  bivalves  (Fig.  81,  3),  there 


valve  and  mantle-lobe,  and  half  the  siphons 
are  removed.  «  s  Respiratory  siphons,  th4 
arrows  indicating  the  direction  of  the  cur- 
rents ;  a  a'  Adductor  muscles ;  6  Gills ;  h 
Heart ;  o  Mouth,  surrounded  by  ( p)  labial 
palpi ;  /  Foot :  v  Anus ;  m  Cut  edge  of  the 
mantle. 


178 


INVERTEBRATE  ANIMALS. 


is  only  one  adductor  muscle,  but  ordinarily  there  are  two  (Fig-. 
81,  2).  These  muscles  leave  distinct  scars  or  "  muscular  im- 
pressions "  in  the  dead  shell,  so  that  it  is  easy  to  determine 
how  many  were  present  in  any  given  shell.  The  margin  of 
the  mantle,  too,  is  muscular,  and  leaves  upon  the  shell  a  dis- 
tinct line  where  it  was  attached,  this  being  known  as  the 
"  pallial  line  "  (Lat.  pallium,  a  mantle),  as  shown  in  Fig.  81. 

As  regards  the  shell  of  the  bivalves,  the  following  are  the 
chief  points  to  be  noticed.  Each  valve  of  the  shell  (Fig.  81) 
is  to  be  regarded  as  essentially  a  hollow  cone,  the  apex  of 
which  is  turned  more  or  less  to  one  side.  The  apex  of  the 
valve  is  known  as  the  "  umbo  "  or  "  beak,"  and  is  turned  tow- 
ard the  mouth  of  the  animal.  Consequently,  the  side  of  the 


FIG.  81. — Shells  of  Lamellibranchiata.  1.  Cydas  amnica,  a  shell  with  two  adductor 
muscles,  and  an  "  entire  "  mantle-margin.  2.  Tapes  pullastra,  a  shell  with  two  adduc- 
tors, and  an  indented  pallial  line.  3.  Perna  ephippiwm,  a  shell  with  one  adductor 
muscle :  a  Pallial  line ;  b  Scars  left  by  the  adductors ;  c  Siphonal  impression. 


shell  toward  which  the  beaks  are  turned  is  known  as  the 
"  anterior  "  side,  and  it  is  usually  much  shorter  than  the  oppo- 
site or  "  posterior  "  side.  The  side  of  the  shell  at  which  the 
beaks  are  situated  is  known  as  the  "  dorsal "  margin  ;  and  here 
the  valves  are  united  to  one  another  for  a  longer  or  shorter 
distance  along  a  line  which  is  known  as  the  "  hinge-line." 
The  union  between  the  valves  is  usually  effected  by  means  of 
interlocking  parts  or  "  teeth,"  and  there  is  often  a  band  of 
horny  fibres  passing  between  the  two  valves  just  behind  the 
beaks.  In  many  cases,  there  is  also  a  series  of  horny  fibres 
placed  perpendicularly  between  the  beaks,  so  as  to  be  com- 
pressed when  the  shell  is  shut.  By  the  elasticity  of  these, 
and  of  the  external  ligament,  when  present,  the  valves  of  the 
shell  are  opened,  without  any  effort  of  the  animal,  simply  by 
relaxing  the  adductor  muscles.  The  valves  are  shut  again  by 
the  contraction  of  the  adductor  muscle  or  muscles. 


MOLLUSCA  PROPER.  179 

As  already  said,  the  margin  of  the  mantle  leaves  on  the 
shell  a  distinct  impression — the  "  pallial  line  " — and,  by  inspec- 
tion of  this,  important  conclusions  can  be  drawn  in  any  given 
case  as  to  the  mode  and  life  of  the  animal.  In  certain  shells, 
namely,  the  pallial  line  (Fig.  81, 1)  is  unbroken  or  "  entire,"  and 
in  these  the  mantle-lobes  were  either  quite  free,  or  if  attached 
to  one  another  and  drawn  out  into  respiratory  tubes,  these 
were  not  furnished  with  special  muscles  by  which  the  tubes 
could  be  retracted  within  the  shell.  In  other  bivalves,  on  the 
other  hand  (Fig.  81,  2),  the  pallial  line  is  indented  to  a  greater 
or  less  extent,  showing  that  the  mantle-lobes  were  more  or 
less  united  to  one  another,  and  were  drawn  out  into  long 
respiratory  tubes  or  siphons,  which  were  furnished  with  spe- 
cial muscles  by  which  they  could  be  withdrawn  within  the  shell. 
This  difference  expresses  a  real  distinction  among  the  bivalves, 
due  to  their  mode  of  life.  In  all  alike,  the  respiratory  organs 
are  in  the  form  of  membranous  leaf-like  gills,  of  which  there 
are  generally  two  on  each  side  of  the  body.  The  gills  are 
composed  generally  of  tubular  rods  (Fig.  80,  b)  richly  supplied 
with  blood-vessels,  and  covered  with  vibrating  cilia.  For  the 
proper  maintenance  of  respiration,  however,  it  is  necessary 
that  the  gills  should  be  constantly  supplied  with  fresh  water. 
In  those  bivalves  in  which  the  animal  is  free  and  the  mantle- 
lobes  not  attached  to  one  another,  this  is  effected  without  any 
special  mechanism.  In  those  forms,  however,  in  which  the 
animal  lives  buried  in  the  mud  and  sand,  and  the  mantle-lobes 
are  more  or  less  completely  united,  there  are  two  orifices,  one 
of  which  admits  fresh  water,  while  the  effete  water  is  got  rid 
of  through  the  other.  These  orifices,  in  the  shells  just  spoken 
of,  are  extended  into  two  long  tubes  which  are  known  as  the 
"respiratory  siphons."  The  water  passes  in  by  one  siphon, 
is  swept  over  the  surface  of  the  gills,  an$  then  reaches  the 
mouth  (Fig.  80,  s  s),  when  it  is  returned  in  the  opposite 
direction  to  escape  by  the  other  siphon.  The  same  current  of 
water,  therefore,  both  carries  oxygen  to  the  gills,  and  serves 
to  convey  food  to  the  mouth.  The  two  siphons  may  be  quite 
distinct  from  one  another,  but  they  are  very  often  united 
together  so  as  to  look  like  a  single  tube  (Fig.  80).  They  are 
often  very  small,  and  then  they  leave  no  traces  of  their  ex- 
istence in  the  dead  shell ;  but,  when  they  are  very  long,  they 
are  furnished  with  muscles  to  retract  them  within  the  shell, 
and  it  is  the  scar  left  by  these  muscles  which  causes  the  pallial 
line  to*  be  indented.  This  indentation,  therefore,  as  seen  in 
the  dead  shell,  is  an  indication  that  the  animal  possessed  long 


180  INVERTEBRATE  ANIMALS. 

retractile  respiratory  siphons,  and  lived,  therefore,  most  prob- 
ably imbedded  in  sand  or  mud. 

There  is  always  a  distinct  heart,  composed  of  two  or  three 
chambers,  and  in  all  cases  acting  as  a  mere  arterial  heart. 
That  is  to  say,  the  heart  propels  the  aerated  blood  derived 
from  the  gills  through  the  body,  and  has  nothing  to  do  with 
the  propulsion  of  the  non-aerated  or  venous  blood  through  the 
gills.  There  is  never  any  distinct  head  in  any  of  the  Bivalves, 
and  for  this  reason  they  are  sometimes  called  the  "  headless  " 
(acephalous)  Mollusks.  The  mouth  is  simply  placed  at  the 
anterior  end  of  the  body,  and  is  never  furnished  with  teeth, 
though  usually  provided  with  membranous  processes  or 
"palpi"  (Fig.  80,  p).  The  mouth  opens  into  a  gullet  which 
conducts  to  a  stomach.  The  intestine  is  convoluted,  and  usu- 
ally perforates  the  ventricle  of  the  heart,  ultimately  terminating 
in  a  distinct  anus,  which  is  always  placed  near  the  respiratory 
aperture.  A  large  and  well-developed  liver  is  also  present. 

The  nervous  system  has  its  normal  form  of  three  principal 
masses — the  cerebral,  the  pedal,  and  the  parieto-splanchnic 
ganglia. 

The  majority  of  the  bivalve  Mollusks  have  the  sexes  dis- 
tinct, but  they  are  sometimes  united  in  the  same  individual. 
The  young  are  hatched  before  they  leave  the  parent,  and, 
when  first  liberated,  are  ciliated  and  free-swimming. 

The  habits  of  the  Lamellibranchiata  are  very  various. 
Some,  such  as  the  Scallops  (Pecten),  habitually  lie  on  one 
side,  the  lower  valve  being  the  deepest,  and  the  foot  rudimen- 
tary or  wanting.  Others  are  fixed  to  the  bottom  of  the  sea 
by  "the  substance  of  one  of  the  valves.  Others,  such  as  the 
common  Mussel,  are  moored  to  some  foreign  object  by  a  tuft 
of  silky  fibres,  constituting  a  "  byssus."  Many,  such  as  the 
Gapers  (My a]  and  Razor-shells  (Solen),  spend  their  existence 
sunk  in  the  sand  of  the  sea-shore  or  the  mud  of  estuaries. 
Others,  such  as  the  Pholades,  bore  holes  in  rock  or  wood,  in 
which  they  live.  Finally,  many  are  permanently  free  and 
locomotive. 

CLASS  II.  GASTEROPODA  (Gr.  gaster,  belly ; podes,  feet). — 
This  class  includes  an  enormous  number  of  Mollusks,  such  as  the 
land-snails,  sea-snails,  whelks,  limpets,  slugs,  sea-lemons,  etc., 
which  agree  in  many  fundamental  characters,  but  nevertheless 
present  many  striking  differences.  From  the  very  common 
occurrence  of  a  shell  composed  of  a  single  piece,  the  Gastero- 
poda are  often  spoken  of  in  a  general  way  as  the  "  univalve  " 


MOLLUSCA  PROPER.  181 

Mollusks.  In  many,  however,  there  is  either  no  shell  at  all,  or 
one  so  small  that  it  would  not  generally  be  recognized  as  such ; 
and  in  a  few  the  shell  is  composed  of  several  pieces  ("  multi- 
valve  ").  In  none,  however,  is  the  shell  composed  of  two 
pieces  or  "  bivalve."  The  great  majority  of  the  Gasteropoda 
are  further  distinguished  by  the  great  development  of  the 
foot,  which  constitutes  a  broad,  flattened  disk  upon  which  they 
creep  about,  as  may  readily  be  observed  in  the  common  slugs. 
Some,  however,  have  the  foot  much  modified  and  adapted  for 
swimming.  In  many  cases,  also,  the  foot  carries  behind  a 
horny  or  shelly  plate  which  is  known  as  the  "  operculum " 
(Fig.  82,  o),  and  which  serves  to  close  the  shell  when  the 
animal  is  withdrawn  within  it. 


•s 


FIG.  82. — Gasteropoda.    Ampullaria  canaUeulata,  one  of  the  Apple-shells : 
o  Operculum ;  s  Eespiratory  siphon. 

The  head  in  most  of  the  Gasteropoda,  unlike  the  Bivalves, 
is  very  distinctly  marked  out,  and  carries  two  long  feelers,  and 
two  eyes,  often  placed  upon  stalks  (Fig.  85).  The  mouth, 
also,  differs  from  that  of  the  Bivalves  in  being  furnished  with  a 
singular  apparatus  of  teeth,  constituting  what  is  known  as 
the  "  odontophore  "  (Fig.  82),  or  "  lingual  ribbon."  This  con- 
sists essentially  of  a  number  of  siliceous  teeth,  of  different 
shapes  in  different  species,  supported  upon  a  kind  of  strap  which 
can  be  made  to  work  backward  and  forward  over  a  cartila- 
ginous cushion,  thus  acting  like  a  chain-saw,  In  addition  to 
the  odontophore  there  are  sometimes  horny  jaws  as  well.  The 
mouth  leads  by  a  gullet  into  a  distinct  stomach,  which  some- 
times is  provided  with  calcareous  plates  for  grinding  down 
the  food,  The  intestine  is  long,  and  always  terminates  in  a 
distinct  anal  aperture.  Distinct  salivary  glands  are  usually 
present,  and  the  liver  is  well  developed. 


182  INVERTEBRATE  ANIMALS. 

A  distinct  heart  is  almost  always  present,  and  consists  of 
two  chambers,  an  auricle  and  a  ventricle.  Respiration  is  very 
variously  effected — one  great  division  being  constructed  to 
breathe  air  by  means  of  water,  while  in  another  section  the 
respiration  is  aerial.  In  the  former  of  these — often  spoken  of 
as  the  "  branchiate  "  Gasteropods — respiration  may  be  carried 
on  in  three  ways  :  Firstly,  there  may  be  no  special  breathing- 
organ,  the  blood  being  simply  exposed  to 
the  astion  of  the  water,  as  it  circulates 
through  the  thin  walls  of  the  mantle-cavity. 
Secondly,  the  breathing-organs  may  be  in 
the  form  of  outward  processes  of  the  skin, 
exposed  to  view  on  the  back  or  sides  of  the 
animal  (Fig.  85).  Thirdly,  the  breathing- 
organs  are  in  the  form  of  plume-like  gills, 
contained  in  a  more  or  less  complete  cham- 
ber, formed  by  a  folding  of  the  mantle.  In 
many  members  of  this  group  the  water  ob- 
tains access  to  the  gill-chamber  by  means  of 
FIG.  83.— Portion  of  the  a  tubular  prolongation  or  folding  of  the 

mantle»  formins a  ^p1?011  (Fis- 82'  *)» and 

Wood"  °^en  ^e  effete  water  is  expelled  by  another 
tube  which  is  similarly  constructed.  In  the 
second  great  section — often  called  the  "pulmonate"  Gaste- 
ropods— respiration  is  effected  by  a  pulmonary  chamber  or  lung, 
formed  by  a  folding  of  a  mantle,  and  having  air  admitted  to 
it  by  a  distinct  aperture. 

The  sexes  in  the  Gasteropoda  are  mostly  distinct,  but  they 
are  sometimes  united  in  the  same  individual.  The  young, 
when  first  hatched,  are  always  provided  with  an  embryonic 
shell,  which  may  be  entirely  lost  in  the  adult,  or  may  simply 
become  concealed  by  a  fold  of  the  mantle.  In  the  water- 
breathing  forms  the  young  is  protected  by  a  small  nautilus- 
shaped  shell,  within  which  it  can  entirely  withdraw.  It  is  en- 
abled to  swim  about  freely  by  means  of  two  ciliated  lobes  spring- 
ing from  the  sides  of  the  head,  and  in  this  stage  it  is  very 
like  the  permanent  adult  condition  of  the  Pteropoda  (Fig.  88). 

As  regards  the  shell  of  the  Gasteropoda,  the  following 
points  may  be  noticed:  The  shell  is  composed  either  of  a 
single  piece  (univalve),  or  of  a  number  of  plates  placed  one 
behind  the  other  (multivalve). 

The  univalve  shell  is  to  be  looked  upon  as  essentially  a 
hollow  cone,  the  apex  of  which  is  placed  a  little  on  one  side. 
In  the  simplest  forms,  as  in  the  Limpets,  the  conical  shell  is 


MOLLUSCA  PROPER. 


183 


retained  throughout  life  without  any  alteration.  In  the  great 
majority  of  cases,  however,  the  cone  is  considerably  elongated 
so  as  to  form  a  tube,  which  may  retain  this  shape  (as  in  the 
"  tooth-shell "),  but  which  is  usually  coiled  up  into  a  spiral. 
The  "  spiral  univalve  "  may,  in  fact,  be  regarded  as  the  typical 


FIG.  84.— Gasteropoda,  a  Shell  of  the  Turritella  communis,  showh>£  &  round  mouth; 
&  Shell  of  the  common  whelk  (Buccinum  undatum\  showing  the  mouth  notched  for 
a  respiratory  siphon. 

form  of  the  shell  in  the  Gasteropoda  (Fig.  84).  The  coils  of 
the  spiral  are  termed  the  "  whorls,"  and  are  usually  more  or 
less  amalgamated  on  one  side.  In  most  cases,  too,  the  whorls 
are  wound  obliquely  round  a  central  axis  or  pillar,  increasing 
gradually  in  size  to  the  mouth.  The  last  whorl  is  the  largest, 
and  is  termed  the  "  body-whorl."  The  mouth  of  the  shell  in 
many  forms  is  unbrokenly  round  or  "  entire'"  (Fig.  84,  a\  and 
it  is  found  that  most  of  these  shells  subsist  upon  vegetable 
food,  as,  for  instance,  the  common  periwinkles.  In  others, 
again  (Fig.  84,  #),  the  mouth  of  the  snell  is  notched  or  is  pro- 
duced into  a  canal,  as  in  the  common  whelk,  and  it  is  found 
that  these  live  upon  animal  food,  or  are  "  carnivorous."  There 
may  be  more  than  one  of  these  canals  or  tubes,  but  they  do 
not  necessarily  indicate  the  nature  of  the  food,  as  their  func- 
tion is  to  protect  the  respiratory  siphons. 

The  Gasteropoda  are  divided  into  a  good  many  groups, 
of  which  the  more  important  may  be  briefly  noticed,  the  fore- 
going applying  chiefly  to  the  ordinary  forms,  which,  therefore, 
need  no  further  description.  The  remaining  members  of  the 


184 


INVERTEBRATE  ANIMALS. 


water-breathing  Gasteropods  are  divided  into  two  sections, 
differing  a  good  deal  from  the  typical  forms  of  the  class  in 
many  respects. 

As  examples  of  the  first  of  these  may  be  taken  the  sea- 
slugs  and  sea-lemons  (Nudibranchi&ta),  specimens  of  which 
may  at  any  time  be  found  creeping  about  on  sea-weeds,  or  at- 
tached to  the  under  surface  of  stones  at  low  water.  These 
slug-like  animals  (Fig.  85)  are  wholly  destitute  of  a  shell  when 

fully  grown,  but  possess  an  em- 
bryonic shell  when  young.  When 
there  are  any  distinct  respiratory 
organs,  these  are  in  the  form  of 
gills,  placed,  without  any  protec- 
tion, upon  the  back  or  sides  of 
the  body.  The  head  is  furnished 
with  tentacles,  which  do  not  ap- 
pear to  be  used  as  organs  of  touch, 
but  are  more  probably  connected  with  the  sense  of  smell ;  and 
behind  the  tentacles  are  generally  two  eyes.  The  nervous 
system  is  extremely  well  developed,,  and  would  lead  to  the  be- 
lief that  the  Sea-slugs  are  among  the  highest  of  the  Gastero- 
poda. Locomotion  is  effected,  as  in  the  true  Slugs,  by  creep- 
ing about  on  the  flattened  foot. 

The  last  remaining  group  of  the  "  branchiate  "  Gasteropods 
is  that  of  the  Heteropoda  (Fig.  86),  comprising  a  number  of 
curious  forms  which  are  found  swimming  at  the  surface  of  the 


FIG.  85. — Nudibranchiata.    Doris  Joihn- 
stoni,  one  of  the  Sea-lemons. 


FIG.  86. — Heteropoda.     Carinaria  cambium;  p  Proboscis  and  mouth; 
*  Tentacles;  g  Gills;  «  Shell; /Foot;  d  Disk  (after  Woodward). 

open  sea,  instead  of  creeping  about  at  the  bottom  of  the  sea. 
In  order  to  adapt  them  for  this  mode  of  life,  the  foot,  instead 
of  forming  a  creeping  disk,  is  modified  to  form  a  compressed 
fin  (/).  The  Heteropoda  are  to  be  regarded  as  the  most 


MOLLUSCA  PROPER.  185 

highly  organized  of  all  the  Gasteropoda,  at  the  same  time  that 
they  are  not  the  most  typical  members  of  the  class.  Some  of 
them  can  retire  completely  within  their  shells,  but  others  have 
large  bodies,  and  the  shell  is  either  small  or  entirely  absent. 
In  Carinaria,  which  may  be  taken  as  a  good  example  of  the 
group,  there  is  a  little  limpet-shaped  shell  protecting  the 
gills  (b)  and  heart.  The  animal  swims,  back  downward,  by 
means  of  a  vertically-flattened  ventral  fin  (/),  on  one  side  of 
which  is  a  little  sucking-disk  (<#),  by  which  the  animal  can  ad- 
here at  pleasure  to  floating  sea-weed.  Carinaria  is  found  in  the 
Mediterranean  and  other  warm  seas,  and  is  so  transparent  that 
the  course  of  the  intestine  can  be  seen  along  its  whole  length. 
The  last  group  of  the  class  is  that  of  the  "  air-breathing  " 
Gasteropods,  so  well  known  as  Land-snails,  Pond-snails,  and 
Slugs  (Fig.  87).  All  the  members  of  this  group  are  formed 
to  breathe  air  directly,  instead  of  through  the  medium  of 
water,  and  they,  therefore,  never  possess  gills  or  branchias. 


FIG.  SI.—Limax  Sowerbyi,  one  of  the  slugs  (after  Woodward). 

In  place  of  these  they  have  a  pulmonary  chamber  or  lung, 
formed  by  a  folding  of  the  mantle,  and  having  air  admitted  to 
it  by  a  round  hole  on  the  right  side  of  the  neck,  which  can  be 
opened  and  closed  at  will.  Though  thus  adapted  for  breath- 
ing air  directly,  many  of  the  members  of  this  group  can  only 
live  in  damp  or  moist  places,  while  others  habitually  live  in 
fresh  water.  The  common  Pond-snails  are  examples  of  these 
last.  The  condition  of  the  shell  varies  much.  Some,  such  as 
the  common  Land-snails,  have  a  well-developed  shell  within 
which  the  animal  can  completely  withdraw  itself  for  protec- 
tion. Others,  such  as  the  common  Slugs  (Fig.  87),  have  a 
rudimentary  shell  which  is  completely  concealed  within  the 
mantle.  Others  are  entirely  destitute  of  a  shell.  They  all 
agree  with  the  typical  Gasteropods  in  creeping  about  on  a 
broad,  flattened  foot. 

CLASS  HI.   PTEEOPODA  (Gr.  pteron,  wing ;  podes,  feet). — 


186 


INVERTEBRATE  ANIMALS. 


This  class  is  a  very  small  one,  and  includes  a  number  of  minute 
oceanic  Mollusks,  which  are  found  swimming  near  the  sur- 
face in  the  open  ocean,  far  from  land,  and  often  in  enormous 
numbers.  The  organs  of  locomotion  are  two  wing-like  fins 
(Fig.  88)  attached  to  the  sides  of  the  head,  and  formed  by  a 


FIG.  88.— Pteropoda.    a  Cleodora  pyramidata  ;  6  Cuvieria  columnella. 
(After  Woodward.) 

modification  of  a  portion  of  the  foot.  The  body  is  usually  pro- 
tected by  a  symmetrical  glassy  shell  (Fig.  88),  consisting  of 
two  plates  united  along  their  edges,  or  in  other  cases  forming 
a  spiral.  In  some,  however,  there  is  no  shell,  and  the  body  is 
quite  naked.  The  head  is  rudimentary,  and  bears  the  mouth, 
which  is  furnished  with  an  odontophore.  The  heart  consists 
of  an  auricle  and  ventricle,  and  the  respiratory  organs  are 
extremely  rudimentary.  The  sexes  are  united  in  the  same 
individual  in  all  the  Pteropoda. 

The  Pteropoda  occur,  as  already  said,  in  the  open  ocean, 
and  they  are  found  in  all  seas  from  the  tropics  to  within  the 
arctic  circle,  sometimes  in  such  numbers  as  to  discolor  the 
water  for  many  miles.  Minute  as  they  are,  they  constitute  in 
high  latitudes  one  of  the  staple  articles  of  diet  of  the  whale, 
and  they  themselves  in  turn  are  probably  carnivorous,  feed- 
ing upon  small  Crustaceans  and  other  diminutive  creatures. 
Though  all  the  living  forms  are  small,  geology  leads  us  to  be- 
lieve that  formerly  there  existed  comparatively  gigantic  forms, 
which  appear  to  be  truly  referable  to  this  class. 


CHAPTER  XXII. 


CEPHALOPODA. 


CLASS  IV.  CEPHALOPODA.  —  The  last  and  highest  class  of 
the  Mollusca  is  that  of  the  Cephalopoda,  comprising  the 
Cuttle-fishes,  Calamaries,  Squids,  and  the  Pearly  Nautilus. 
They  are  all  inhabitants  of  the  sea, 
and  are  all  carnivorous  ;  and  they  are 
possessed  of  considerable  powers 
of  locomotion.  At  the  bottom  of 
the  sea  they  can  walk  about,  head 
downward,  by  means  of  the  arms 
(Fig.  89),  which  surround  the 
mouth,  which  are  usually  provided 
with  numerous  suckers,  and  which 
are  really  produced  by  a  splitting 
up  of  the  margin  of  the  foot.  It  is 
from  the  presence  of  these  arms 
that  the  class  derives  its  name  (Gr. 
Jcephale,  head  ;  and  joocfes,  feet).  The 
Cuttle-fishes  can  also  swim  rapid- 
ly, either  by  means  of  expansions 
of  the  skin  constituting  fins,  or  by 
the  forcible  expulsion  of  water 
from  the  cavity  of  the  mantle,  the 
reaction  of  which  causes  the  animal 
to  move  in  the  opposite  direction. 
The  majority  of  the  living  Cephalo- 
pods  are  naked,  possessing  only  an 
internal  skeleton,  and  this  often  a 

rudimentary  one  ;  but  the  Argonaut  (Paper  Nautilus)  and  the 

an  external  shell,  though 
Ferent  in  the  two  forms. 


8d,_Sepioia  Atlanta,  one  of 
the  Cuttle-  fishes  (after  Wood- 


A   Ui.VAJLU.A\_/JJLL/C**l    ¥       UUW    •         IJIAV      LM.J.Vy     •UUf&VrUCVW 

Pearly  Nautilus  are  protected  by 
the  nature  of  this  is  extremely  diffe 


188  INVERTEBRATE  ANIMALS. 

The  body  in  the  Cephalopoda  is  symmetrical,  and  is  en 
closed  in  an  integument  which  may  be  regarded  as  a  modificaN 
tion  of  the  mantle  of  the  other  Mottusca.  Ordinarily  there  it» 
a  tolerably  distinct  division  of  the  body  into  an  anterior  por- 
tion, carrying  the  head,  and  a  posterior  portion,  in  which 
the  internal  organs  are  enclosed.  The  head  (Fig.  89)  is 
very  distinct,  bearing  a  pair  of  large  globular  eyes,  and 
having  the  mouth  in  its  centre.  The  mouth  is  surrounded 
by  a  circle  of  eight,  ten,  or  more,  long  muscular  processes, 
or  arms,  which  are  generally  provided  with  rows  of  suckers. 
Each  sucker  consists  of  a  cup-shaped  cavity,  the  muscular 
fibres  of  which  converge  to  the  centre,  where  there  is  a 
little  muscular  eminence.  When  the  sucker  is  applied  to  any 
surface,  the  contraction  of  the  radiating  muscular  fibres  de- 
presses the  central  eminence  so  as  to  produce  a  vacuum  below 
it,  and  in  this  way  each  sucker  acts  most  efficiently  as  an  ad- 
hesive organ.  The  whole  of  this  complex  mechanism  of  suckers 
is  completely  under  the  control  of  the  animal,  and  the  ir- 
ritability of  the  suckers  is  retained  even  for  days  after  death. 
In  most  of  the  Cuttle-fishes  ( Octopoda)  there  are  only  eight 
arms,  and  these  are  nearly  similar  to  one  another.  In  others, 
however  (Fig.  89),  there  are  ten  processes  round  the  mouth, 
of  which  eight  are  like  each  other,  and  constitute  the  true 
arms,  while  two — called  tentacles — are  much  longer  than  the 
others,  and  bear  suckers  only  toward  their  extremities,  which 
are  enlarged  and  club-shaped.  The  Paper  Nautilus  (Fig.  90) 
has  two  of  the  arms  webbed  at  their  extremities  and  secreting 
a  shell ;  and  the  Pearly  Nautilus,  alone  of  all  living  Cephalo- 
poda, has  numerous  arms,  more  than  ten  in  number,  and 
destitute  of  suckers. 

The  mouth  leads  into  a  cavity  containing  two  powerful 
horny  or  partially  calcareous  jaws  working  vertically,  very 
like  the  beak  of  a  bird,  together  with  an  "  odontophore "  or 
"  tongue,"  the  hinder  part  of  which  is  furnished  with  recurved 
spines.  This  cavity  leads  by  a  gullet,  furnished  with  salivary 
glands,  into  a  stomach,  from  which  an  intestine  is  continued 
to  terminate  by  a  distinct  anus,  which  opens  on  the  ventral 
surface  at  the  base  of  the  so-called  "  funnel."  The  funnel  is  a 
muscular  tube  placed  on  the  under  surface  of  the  head,  and 
communicating  on  the  one  hand  with  the  external  medium, 
and  on  the  other  with  the  cavity  of  the  mantle.  In  the  Naw- 
tilus  alone  it  is  simply  formed  of  two  muscular  lobes,  which 
are  in  apposition,  but  are  not  united  together  so  as  to  form  a 
tube.  In  many  cases  there  is  also  a  special  gland,  known  as 


CEPHALOPODA.  189 

the  "  ink-bag,"  for  the  secretion  of  an  inky  fluid,  which  the 
animal  discharges  into  the  water,  so  as  to  enable  it  to  escape 
when  menaced  or  pursued.  The  duct  of  the  ink-bag  opens  at 
the  base  of  the  funnel  near  the  anus,  but  the  Pearly  Nautilus 
and  the  allied  fossil  forms  are  without  this  means  of  defence, 
which  the  presence  of  an  external  shell  renders  unnecessary. 

The  respiratory  organs  are  in  the  form  of  plume-like  gills, 
placed  on  the  sides  of  the  body  in  a  branchial  chamber,  which 
opens  in  front  on  the  under  surface  of  the  body.  In  almost 
all  the  living  Cephalopoda  there  are  only  two  gills,  one  on 
each  side,  and  hence  this  section  is  known  as  that  of  the 
" Dibranchiata"  In  the  Pearly  Nautilus  alone  there  are  four 
gills,  two  on  each  side,  hence  the  name  of  "  Tetrabranchiata" 
applied  to  the  order  of  which  this  is  the  only  living  represent- 
ative. In  the  Cuttle-fishes,  at  the  base  of  each  gill  is  a  special 
contractile  cavity,  called  a  "  branchial  heart,"  by  which  the 
venous  blood,  returned  from  the  body,  is  driven  through  the 
gills.  In  addition  to  these  branchial  hearts  there  is  a  true 
arterial  heart,  by  which  the  aerated  blood  received  from  the 
gills  is  driven  through  the  body.  The  admission  of  water  to 
the  branchiae  is  effected  by  the  expansion  of  the  mantle,  which 
allows  the  entrance  of  the  outer  water  into  the  mantle-cavity. 
The  mantle  then  contracts,  and  the  water  is  forcibly  expelled 
through  the  funnel,  which  is  often  furnished  with  a  valve,  al- 
lowing the  passage  of  water  outward,  but  preventing  its  en- 
trance inward.  By  a  repetition  of  this  process  both  respira- 
tion and  locomotion  are  simultaneously  effected,  for  the  jets 
of  water^expelled  from  the  funnel  by  their  reaction  drive  the 
animal  in  the  opposite  direction.  In  this  case,  therefore,  as  in 
many  others,  the  more  active  the  animal  is,  the  more  perfectly 
is  the  respiratory  process  carried  on. 

The  nervous  system  is  formed  upon  essentially  the  same 
plan  as  in  the  other  Mollusca^  but  the  cerebral  ganglia  are 
protected  by  a  cartilage,  which  is  to  be  regarded  as  a  rudimen- 
tary skull.  This  structure,  therefore,  is  a  decided  approach  to 
the  Vertebrate  type  of  organization. 

The  sexes  in  all  the  Cephalopoda  are  in  different  individ- 
uals, and  the  reproductive  process  in  the  Cuttle-fishes  is  at- 
tended with  some  singular  phenomena.  The  most  remarkable 
point  in  this  connection  is  the  modification  of  one  of  the  arms 
of  the  male  Cuttle-fishes,  for  the  purpose  of  conveying  the 
male  element  to  the  female.  The  details  of  the  modification 
vary  in  different  species  of  Cuttle-fish. 

In  some  species  one  arm  is  simply  so  modified  as  to  be 


190  INVERTEBRATE  ANIMALS. 

able  to  transmit  the  sperm-cells  to  the  female,  but  it  remains 
permanently  attached  to  the  animal.  In  the  Paper  Nautilus 
(Argonaut)  the  process  goes  still  further.  The  female  of  this 
species  (Fig.  90)  attains  a  considerable  size,  and  is  protected 
by  an  external  shell.  The  male  is  not  more  than  an  inch  in 
length,  is  devoid  of  a  shell,  and  has  its  third  left  arm  meta- 
morphosed. This  arm  is  developed  in  a  cyst,  and  is  ultimately 
detached  from  the  body,  and  deposited  by  the  male  within 
the  mantle-cavity  of  the  female.  When  first  discovered  in  this 
position,  it  was  described  as  a  worm  living  parasitically  on 
the  Argonaut,  under  the  name  of  "  Hectocotylus  "  (Gr.  hekaton, 
a  hundred ;  and  kotulos,  a  cup),  from  the  suckers,  or  cups,  with 
which  it  was  furnished.  Subsequently  it  was  described  as  the 
entire  male  Argonaut ;  and  it  is  only  recently  that  it  has  been 
proved  to  be  nothing  more  than  one  of  the  arms  of  the  male, 
detached  for  the  purpose  of  conveying  the  sperm-cells  to  the 
female. 

The  shell  of  the  Cephalopoda  is  sometimes  external,  some- 
times internal.  The  internal  skeleton  is  seen  in  the  various 
Cuttle-fishes,  in  which  it  is  known  as  the  "  cuttle-bone "  or 
"  pen."  It  may  be  either  horny  or  calcareous,  and  it  is  some- 
times complicated  by  the  addition  of  a  chambered  portion. 
The  only  living  Cephalopods  which  are  provided  with  an  ex- 
ternal shell  are  the  Paper  Nautilus  (Argonauta)  and  the 
Pearly  Nautilus  (Nautilus  pompilius)  ;  but  not  only  is  the 
structure  of  the  animal  different  in  each  of  these,  but  the 
nature  of  the  shell  itself  is  entirely  different.  The  shell  of 
the  Argonaut  (Fig.  90)  is  coiled  into  a  spiral,  but  it  is  not  di- 
vided into  chambers,  and  it  is  secreted  by  the  webbed  extrem- 
ities of  two  of  the  dorsal  arms  of  the  female.  These  arms 
are  bent  backward,  so  as  to  allow  the  animal  to  live  in  the 
shell ;  but  there  is  no  organic  connection  between  the  shell  and 
the  body  of  the  animal.  The  shell  of  the  Pearly  Nautilus,  on 
the  other  hand,  is  secreted  by  the  mantle,  and  is  organically 
connected  to  the  animal.  It  is  coiled  into  a  spiral  (Fig.  91), 
but  it  differs  from  the  shell  of  the  Argonaut  in  being  divided 
into  a  series  of  chambers  by  means  of  shelly  partitions,  which 
are  connected  together  by  a  tube  or  "  siphuncle,"  the  animal 
itself  living  in  the  last  and  largest  chamber  only  of  the  shell. 

The  Cephalopoda  are  divided  into  two  extremely  dis- 
tinct and  natural  orders,  termed  respectively  Dibranchiata  and 
Tetrabranchiata,  according  as  they  have  two  or  four  gills  or 
branchiae. 

The  Dibranchiata  comprise  the  Cuttle-fishes,  Squids,  Cala- 


CEPHALOPODA.  191 

maries,  and  Paper  Nautilus,  and  they  are  characterized  by 
being  almost  invariably  destitute  of  any  external  shell ;  by 
never  having  more  than  eight  or  ten  arms,  which  are  always 
furnished  with  suckers ;  by  having  only  two  gills,  which  are 
provided  with  "  branchial  hearts ; "  by  the  possession  of  an 
"  ink-bag ;  "  and  by  the  fact  that  the  "  funnel "  forms  a  com- 
plete tube.  They  are  divided  into  two  sections —  Octopoda 
and  Decapoda — according  as  they  have  only  eight  arms,  or 
eight  arms  with  two  additional  longer  processes  or  "tentacles  " 
(Fig.  89).  Among  the  Octopoda  are  the  Paper  Nautilus  and 
the  Poulpes  ( Octopus).  The  Paper  Nautilus  is  found  in  the 
warmer  seas  of  various  parts  of  the  world,  generally  floating 
at  the  surface.  The  two  sexes  differ,  as  already  said,  greatly 
in  external  appearance.  The  female  (Fig.  90)  inhabits  a  beau- 


FIG.  90.— Argonauta  argo,  the  Paper  Nautilus,  female.  The  animal  is  represented  in  its 
shell,  but  the  webbed  dorsal  arms  are  separated  from  the  shell  which  they  secrete,  and 
•which  they  ordinarily  embrace. 

tiful  one-chambered  shell,  which  is  secreted  by  the  webbed  ex- 
tremities of  two  of  the  dorsal  arms.  The  shell  is  not  in  any 
way  attached  to  the  body  of  the  animal,  but  the  webbed  arms 
are  turned  backward,  and  the  animal  sits  in  the  shell  with  the 


192  INVERTEBRATE  ANIMALS. 

funnel  turned  toward  the  keel.  It  swims  by  the  jets  of  water 
emitted  from  the  funnel,  and  crawls  upon  the  sea-bottom,  head 
downward,  carrying  its  shell  on  its  back.  The  male  Argonaut 
is  only  about  an  inch  in  length,  has  no  shell,  and  has  all  its 
arms  alike,  except  the  one  which  is  metamorphosed  into  the 
"  hectocotylus."  The  Poulpes  ( Octopi)  are  universally  dis- 
tributed in  the  seas  of  both  temperate  and  tropical  regions. 
They  are  the  "  polypi "  of  Homer  and  Aristotle,  and  are  vo- 
racious animals  inhabiting  rocky  shores. 

The  Decapoda  are  chiefly  found  in  the  open  sea,  often  in 
enormous  numbers,  and  the  best  known  are  the  Calamaries 
and  Squids.  The  body  is  elongated,  and  is  always  furnished 
with  lateral  fins,  with  which  they  swim  actively.  The  shell  is 
internal,  and  differs  considerably  in  different  members  of  the 
group.  To  this  section  of  the  Dibranchiata  belong  the  sin- 
gular fossil  forms  which  are  known  to  the  geologist  as  Belem- 
nites.  These  singular  forms  are  known  almost  solely  by  their 
complicated  internal  skeleton,  and  they  appear  to  have  abound- 
ed in  the  seas  of  the  Secondary  period. 

The  second  order  of  the  Cephalopoda — that  of  the  Tetra- 
branchiata — comprises  forms  characterized  by  being  creeping 
animals,  protected  by  an  external,  many-chambered  shell,  the 
partitions  between  the  chambers  being  perforated  for  the  pas- 
sage of  a  membranous  or  calcareous  tube,  termed  the  "  si- 
phuncle." The  arms  are  more  than  ten  in  number,  and  are 
devoid  of  suckers ;  the  gills  are  four  in  number,  two  on  each 
side  of  the  body ;  the  funnel  does  not  form  a  complete  tube ; 
and  there  is  no  ink-bag. 

Though  abundantly  represented  by  many  and  varied  fossil 
forms,  the  only  living  member  of  the  Tetrabranchiata  with 
which  we  are  acquainted  is  the  Pearly  Nautilus,  which  has 
long  been  known  by  its  beautiful  chambered  shell.  The  shell 
of  the  Pearly  Nautilus  (Fig.  91)  is  coiled  into  a  spiral,  and  is 
many-chambered,  the  chambers  being  walled  off  from  one  an- 
other by  curved  shelly  partitions  or  septa,  perforated  centrally 
by  a  foramen  which  transmits  a  membranous  tube  or  siphuncle. 
The  animal  inhabits  only  the  last  and  largest  chamber  of  the 
shell,  from  which  it  can  protrude  its  head  at  will.  The  func- 
tion of  the  chambers  of  the  shell  is  not  very  clearly  under- 
stood ;  but  it  appears  to  be  that  of  reducing  the  specific  grav- 
ity of  the  shell  to  near  that  of  the  surrounding  water ;  since 
they  appear  to  be  filled  with  some  gas  apparently  secreted  by 
the  animal.  The  siphuncle  does  not  communicate  in  any  way 
with  the  chambers  of  the  shell,  and  its  functions  are  also  un- 


CEPHALOPODA. 


193 


known,  except  that  it  must  certainly  serve  to  maintain  the 
vitality  of  the  shell. 


FIG.  91.— The  Pearly  Nautilus  (Nautilus  pompitius).  a  Mantle ;  &  Its  dorsal  fold ;  c  Hood; 
o  Eye ;  t  Tentacles ;  /  Funnel. 

Of  the  fossil  Tetrabranchiata  the  most  important  are  the 
Orthocerata  and  the  Ammonites.  The  Orthocerata  (Fig.  92) 
played  a  very  important  part  in  the  seas  of  the  Palaeozoic  or 
Ancient-life  period  of  the  earth's  history,  in  which  they  ap- 
parently filled  the  place  now  taken  by  the  predacious  cuttle- 


FIG.  92.—Orthocera8  arplorator.    1.  Side  view  of  a  fragment,  showing  the  edges  of  the 
septa.    2.  Transverse  section  of  the  same,  showing  the  siphuncle  (s).    (Billings.) 

fishes.  They  agreed  with  the  Nautilus  in  having  a  many- 
chambered  shell,  divided  by  curved  partitions,  perforated  by  a 
tube  or  siphuncle.  The  shell,  however,  differed  from  that  of 
the  Nautilus  in  not  being  curved  or  coiled  up,  but  in  being 


194  INVERTEBRATE  ANIMALS. 

straight.  In  other  nearly-allied  forms  the  shell  was  bent  or 
even  partially  coiled  up,  but  never  so  completely  as  in  the 
true  Nautilus.  Many  of  the  Orthocerata  were  of  small  size, 
but  some  of  them  were  colossal,  shells  having  been  found  of 
six  or  seven  feet  in  length,  and  as  thick  as  the  body  of  a  man. 
The  Ammonites,  with  a  number  of  allied  forms  of  varied 
shapes  and  beautiful  structure,  appear  to  have  taken  the  place 
of  the  Nautilidde,  to  a  great  extent,  in  the  seas  of  the  Second- 
arjr  period ;  at  which  time,  too,  Dibranchiate  Cephalopods  first 
made  their  appearance.  The  true  Ammonites  resembled  the 
Nautilus  in  having  a  many-chambered  shell,  which  was  coiled 
up  into  a  spiral,  but  the  position  of  the  siphuncle  was  differ- 
ent, and  the  partitions  or  septa  between  the  various  chambers 
of  the  shell  were  wonderfully  folded  and  lobed  instead  of 
being  simply  curved.  The  numerous  beautiful  shells  allied  to 
the  Ammonites  cannot  be  even  mentioned  here ;  but  it  is  to 
be  remembered  that  they  are  almost  all  characteristic  of  the 
Secondary  period  in  geology,  and  that  they  are  hardly  known 
as  occurring  in  the  older  period  (Palaeozoic  epoch). 


VERTEBRATE  ANIMALS. 


CHAPTER  XXIII. 

GENEEAL  CHAEACTEES  OF  THE  YEETEBEATA. 

THE  five  sub-kingdoms  which  we  have  previously  consid- 
ered, namely,  the  Protozoa,  Codenterata,  Annuloida,  Annu- 
losa,  and  Mottusca,  were  grouped  together  by  Lamarck  into 
one  great  division,  which  he  termed  the  Tnvertebrata.  The 
remaining  sub-kingdom,  that  of  the  Vertebrata,  is  so  well 
marked  and  compact  a  division,  and  its  distinctive  characters 
are  so  numerous  and  so  important,  that  this  mode  of  viewing 
the  animal  kingdom  is,  at  any  rate,  a  very  convenient  one. 

The  sub-kingdom  Vertebrata  includes  the  five  great  classes 
of  the  Fishes  (Pisces),  Amphibians,  Reptiles,  Birds  (Aves), 
and  Mammals ;  and  the  name  of  the  sub-kingdom  is  derived 
from  the  very  general,  though  not  universal,  presence  of  the 
bony  axis  known  as  the  "vertebral  column"  or  backbone. 
One  of  the  most  fundamental  of  the  distinctive  characters  of 
Vertebrate  animals  is  to  be  found  in  the  fact  that  the  main 
masses  of  the  nervous  system  (that  is  to  say,  the  brain  and 
spinal  cord)  are  completely  shut  off  from  the  general  cavity 
of  the  body.  In  all  Invertebrate  animals  (Fig.  93,  A),  the 
body  may  be  regarded  as  a  single  tube,  enclosing  all  the  vis- 
cera ;  and,  consequently,  when  a  distinct  nervous  system  and 
alimentary  canal  are  present,  these  are  in  no  way  shut  off 
from  one  another.  The  transverse  section,  however,  of  any 
Vertebrate  animal  (Fig.  93,  B)  shows  two  tubes,  one  of  which 
contains  the  great  nervous  axis  (•»')  or  brain  and  spinal  cord, 
while  the  other  contains  the  alimentary  canal,  the  chief  circu- 
latory organs,  and  certain  portions  of  the  nervous  system  (ri), 


196 


VERTEBRATE  ANIMALS. 


which  are  known  to  anatomists  as  the  "  sympathetic  "  system. 
Leaving  the  brain  and  spinal  cord  out  of  sight  for  a  mo- 
ment, we  see  that  the  lower  or  visceral  tube  of  a  Vertebrate 
animal  contains  the  digestive  canal  (#),  the  blood-vascular  sys- 
tem (c),  and  a  system  of  nervous  ganglia  (ri).  Now,  this  is 


FIG.  93. — Diagrams  representing  transverse  sections  of  one  of  the  higher  Invertebrata,  A, 
and  one  of  the  Vertebrata,  B.  a  Wall  of  the  body;  b  Alimentary  canal;  c  Haemal  or 
blood-vascular  system ;  n  Nervous  system ;  n'  Cerebro-spinal  axis,  or  brain  and  spinal 
cord,  enclosed  in  a  separate  tube;  ch  Notochord,  or  chorda  dorsalis. 


exactly  what  is  contained  within  the  visceral  cavity  of  any 
Invertebrate  animal ;  and  it  follows  from  this  that  it  is  the 
"  sympathetic "  system  of  Vertebrate  animals  which  is  truly 
comparable  with  the  nervous  system  of  the  Invertebrata.  The 
brain  and  spinal  cord,  or  "  cerebro-spinal  axis,"  are  to  be  looked 
upon  as  something  not  represented  at  all  in  the  Invertebrata. 

Another  peculiarity  which  is  present  in  all  the  Vertebrata 
is,  that  at  an  early  period  of  life  there  is  developed,  in  the  low- 
er wall  of  the  tube  which  contains  the  cerebro-spinal  axis,  a 
singular  structure  known  as  the  "  notochord  "  (Gr.  notos,  back ; 
chorde,  string)  (Fig.  93,  B,  ch).  This  is  a  semi-gelatinous  rod, 
tapering  at  both  ends,  and  extending  along  the  floor  of  the 
cerebro-spinal  tube.  In  some  cases,  the  notochord  remains 
permanently  in  this  condition,  but,  in  most  cases,  it  is  replaced 
at  maturity  by  the  bony  column  or  backbone,  from  which  the 
Vertebrata  derive  their  name.  The  general  structure  of  the 
vertebral  column  will  be  described  shortly,  and  it  is  sufficient 
to  state  here  that  it  consists  of  a  series  of  more  or  less  com- 
pletely bony  segments  or  "  vertebrae,"  arranged  so  as  to  form 
a  longitudinal  axis  upon  which  the  spinal  cord  is  supported. 
It  is  to  be  remembered,  however,  that  all  Vertebrate  animals 
do  not  possess  a  vertebral  column.  They  all  possess  a  noto- 
chord, but  this  may  remain  persistent  throughout  life,  and,  in 
many  cases,  the  development  of  the  spinal  column  is  very  im- 
perfect. 


GENERAL  CHARACTERS   OF  THE  VERTEBRATA.         197 

The  skeleton  of  all  Vertebrate  animals  is  internal,  and  the 
muscles  are  attached  to  its  several  parts.  The  value  of  this 
character  is  in  no  way  affected  by  the  fact  that  many  Verte- 
brates, such  as  the  Tortoises,  Crocodiles,  and  others,  possess 
an  external  skeleton  as  well.  The  limbs  of  Vertebrate  ani- 
mals are  always  articulated  or  jointed  to  the  body,  and  they 
are  always  turned  away  from  that  side  of  the  body  (the  "  neu- 
ral "  side)  upon  which  the  great  masses  of  the  nervous  system 
are  placed.  The  limbs  may  be  altogether  wanting,  or  partial 
ly  undeveloped,  but  there  are  never  more  than  two  pairs,  and 
they  always  have  an  internal  skeleton  for  the  attachment  of 
the  muscles  of  the  limb. 

A  distinct  blood-vascular  system  is  present  in  all  Ver^ 
tebrates,  and  in  all  except  one — the  Lancelet — there  is  a 
single  contractile  cavity  or  heart,  furnished  with  valvular  open- 
ings. 

Lastly,  the  masticatory  organs  of  all  Vertebrates  are  modi- 
fications of  parts  of  the  walls  of  the  head,  and  are  never 
modified  limbs  or  hard  structures  developed  in  the  mucous 
membrane  of  the  digestive  tube,  as  they  are  in  the  Inverte- 
brates. 

The  above  are  the  leading  characters  which  distinguish  the 
Vertebrata  as  a  whole,  and,  before  going  on  to  consider  the 
different  classes,  it  may  be  as  well  to  give  a  short  and  general 
sketch  of  the  anatomy  of  the  Vertebrates,  commencing  with 
their  bony  framework  or  skeleton. 

The  skeleton  of  the  Vertebrata  may  be  regarded  as  con- 
sisting of  the  bones  which  go  to  form  the  trunk  and  head  on 
the  one  hand,  and  of  those  which  form  the  supports  for  the 
limbs  on  the  other  hand.  The  bones  of  the  trunk  and  head 
may  be  regarded  as  essentially  composed  of  a  series  of  bony 
rings  or  segments,  arranged  longitudinally.  Anteriorly,  these 
segments  are  much  expanded  and  also  much  modified  to  form 
the  bony  case  which  encloses  the  brain  and  which  is  termed 
the  cranium  or  skull.  Behind  the  head,  the  segments  enclose 
a  much  smaller  cavity  in  which  is  contained  the  spinal  cord, 
and  they  are  arranged  one  behind  the  other,  forming  the  "  ver- 
tebral column."  The  segments  which  form  the  vertebral 
column  are  called  "  vertebras,"  and  they  have  the  following 
general  structure :  Each  vertebra  (Fig.  94,  A)  consists  of  a 
central  portion  known  as  the  "body,"  or  "centrum"  (c), 
placed  immediately  below  the  spinal  cord,  and  giving  origin  to 
certain  "  processes."  The  ends  of  the  bodies  of  the  vertebrse 
are  all  united  together  in  different  ways,  so  as  to  give  the  col- 


198 


VERTEBRATE  ANIMALS. 


FIG.  94.— A.  Vertebra  (lumbar)  of  the  whale,  c  Centrum  or  body;  n  Neural  arches; 
8  Spinous  process ;  a  Articular  process ;  d  Transverse  processes.  B.  Thoracic  segment 
or  vertebra,  c  Centrum  of  vertebra ;  n  Neural  arches,  enclosing  the  canal  for  the  spinal 
cord  ;  e  Spinous  process ;  r  Eibs ;  p  Costal  cartilages ;  b  Breastbone  or  sternum.  (After 
Owen.) 

umn  great  flexibility.  -  From  the  back  of  the  body  of  the  ver- 
tebra proceed  two  bony  arches  which  unite  behind  and  thus 
form  with  the  centrum  a  bony  canal  in  which  the  spinal  cord 
is  contained.  For  this  reason,  these  arches  (n)  are  called  the 
"  neural "  arches.  From  the  point  where  the  neural  arches 
unite — that  is  to  say,  from  the  back  of  the  neural  canal — pro- 
ceeds a  long  process,  sometimes  cleft  at  its  extremity,  termed 
the  "spinous  process"  (s).  Springing  also  from  each  neural 
arch  is  a  second  shorter  process  (a)  termed  the  "  articular  pro- 
cess," since  by  means  of  these,  as  well  as  by  the  bodies,  the 
vertebrae  are  jointed  or  "  articulated  "  together.  Also  arising 
from  the  neural  arches  at  their  junction  with  the  body  of  the 
vertebra,  there  may  be  two  lateral  processes  (d)  which  are 
called  "  transverse  processes."  This  is  the  ordinary  structure 
of  the  vertebra  of  a  Mammal,  and  the  names  here  used  are 
those  applied  to  the  parts  of  the  vertebra  in  human  anatomy. 
In  philosophical  anatomy,  however,  these  parts  have  proper 
technical  names  which  can  be  employed  for  them  in  all  animals 
alike.  The  nature  of  this  work,  however,  will  not  allow  of 
the  introduction  of  these  here. 

In  the  typical  vertebra  the  segment  is  completed  by  a 
second  arch,  which  is  placed  in  front  of  or  beneath  the  body 
of  the  vertebra,  and  which  is  known  as  the  "  haemal "  arch,  as 
it  includes  and  protects  the  principal  organs  of  the  blood  cir- 
culation (Fig.  94,  B).  This  second  arch  is  often  only  recog- 


GENERAL   CHARACTERS   OF  THE  VERTEBRATA.         199 

nizable  with  great  difficulty,  as  its  parts  are  generally  much 
modified ;  but  a  good  example  may  be  obtained  in  the  human 
chest.  Here,  attached  to  the  front  of  the  vertebrae,  we  find  a 
series  of  bony  arches,  known  as  the  ribs  (r),  followed  by  a 
series  of  cartilaginous  pieces  of  a  similar  shape,  termed  the 
"  costal  cartilages  "  (p),  the  whole  united  in  front  by  a  central 
bone,  known  as  the  breastbone  or  "  sternum  "  (£). 


FIG.  95.— Skeleton  of  the  Beaver  (Castor  fiber),  showing  the  regions  of  the  vertebra 
column,  c  Cervical  region,  or  region  of  the  neck ;  d  Dorsal  region,  or  region  of  the 
back ;  b  Lumbar  region,  or  region  of  the  loins ;  s  Sacrum ;  t  Caudal  region,  or  region 
of  the  tail. 


As  a  general  rule,  among  the  higher  Vertebrates,  the  fol- 
lowing regions  may  be  recognized  in  the  vertebral  column : 
Firstly,  the  cervical  region  (Fig.  95,  c),  comprising  a  variable 
number  of  vertebras,  which  constitute  the  neck,  and  immedi- 
ately follow  the  head.  Secondly,  the  cervical  region  is  suc- 
ceeded by  a  variable  number  of  vertebrae  which  usually  carry 
ribs,  and  are  known  as  the  dorsal  vertebrae  (d\  or  vertebrae 
of  the  back.  Thirdly,  come  certain  vertebrae  which  constitute 
the  lumbar  region  (0),  or  the  region  of  the  loins.  Fourthly, 
there  usually  follows  a  series  of  vertebrae  which  are  immova- 
bly united  together  to  form  a  single  bone,  which  is  termed  the 
sacrum  (s).  Lastly,  there  comes  a  variable  series  of  vertebras 


200 


VERTEBRATE  ANIMALS. 


which  are  usually  free  and  movable  upon  one  another,  and 
which  constitute  the  caudal  region,  or  the  region  of  the  tail  (t). 
The  nature  of  the  bones  which  enter  into  the  composition 
of  the  limbs  varies  somewhat  in  different  Vertebrates  in  ac- 
cordance with  their  mode  of  life ;  but  in  all  the  higher  mem- 
bers of  the  sub-kingdom  the  limbs  are  built  upon  a  general 


FIG.  96.— Fore-limb  of  the  Chimpanzee,  c  Collar-      FIG.  97.— Hind-limb  of  the  Chimpan 


bone,  or  clavicle ;  «  Shoulder-blade,  or  scapu- 
la ;  b  Bone  of  the  upper  arm,  or  humerus ;  r 
Badius ;  u  Ulna ;  d  Bones  of  the  wrist,  or  car- 
pus ;  m  Bones  of  the  root  of  the  hand,  or  me- 
tacarpus ;  p  Bones  of  the  digits,  or  phalanges. 


zee.  i  Innominate  bone ;  /  Thigh- 
bone, or  femur ;  t  Tibia  ;  s  Fibula ; 
r  Bones  of  the  ankle,  or  tarsus ;  m 
Metatarsus ;  p  Phalanges. 


and  easily-recognizable  type.  The  fore-limb  consists  generally 
of  the  following  parts :  1.  A  series  of  bones  uniting  the  limb 
to  the  trunk,  the  two  most  important  being  the  shoulder 
blade  (scapula)  and  the  collar-bone  (clavicle)  (Fig.  96,  s  and  c), 
2.  The  bone  which  forms  the  upper  portion  of  the  limb  proper, 
and  which  is  known  as  the  humerus  (b).  3.  Two  bones  which 
form  the  lower  portion  of  the  limb  (e.  g.,  the  forearm  in  man), 


GENERAL   CHARACTERS  OF  THE  VERTEBRATA.         201 

and  which  are  known  as  the  radius  and  ulna  (r  and  u\  of 
which  the  former  is  the  bone  mainly  concerned  in  carrying  the 
hand  or  fore-foot.  4.  A  number  of  small  bones,  which  form 
the  wrist,  and  are  termed  the  carpus  (d).  5.  The  cylindrical 
bones  (usually  five  in  number)  which  form  the  root  of  the 
hand,  and  are  known  as  the  metacarpus  (m).  6.  The  bones 
which  form  the  fingers  proper,  and  which  are  known  as  the 
phalanges  (p). 

Essentially  the  same  parts  can  be  traced  in  the  hind-limb 
of  a  typical  Vertebrate  animal,  but  they  are  known  by  differ- 
ent names.  The  bones  which  unite  the  limb  to  the  trunk  are 
usually  more  or  less  completely  united  together,  constituting 
a  single  mass,  known  as  the  innominate  bone  (Fig.  97,  i). 
This  is  followed  by  a  long,  cylindrical  bone,  which  forms  the 
upper  portion  of  the  hind-limb,  and  is  known  as  the  "  thigh- 
bone," or  femur  (/*).  Following  this  are  the  two  bones  of 
the  shank,  corresponding  to  the  radius  and  ulna  of  the  fore- 
limb,  and  known  as  the  tibia  and  fibula  (t  and  s).  Of  these, 
the  tibia  (t)  corresponds  to  the  radius,  and  is  mainly  con- 
cerned in  carrying  the  foot.  Next  comes  a  series  of  small 
bones,  which  form  the  ankle,  and  are  known  as  the  tarsus  (r). 
This  is  succeeded  by  a  series  of  cylindrical  bones  (usually  five  in 
number),  which  form  the  root  of  the  foot,  and  which  are  termed 
the  metatarsus  (m).  Finally,  the  metatarsus  is  succeeded 
by  the  bones  of  the  toes,  which  in  this  case  are  again  termed 
the  phalanges  (p).  In  both  limbs  the  usual  number  of  pha- 
langes to  each  toe  or  "  digit "  is  three. 

The  digestive  system  of  the  Vertebrata  does  not  require  a 
lengthened  notice.  The  mouth  is  usually  furnished  with  teeth, 
which  have  for  their  chief  function  the  reduction  of  the  food 
to  a  condition  in  which  it  can  be  digested.  In  some  animals, 
however,  such  as  the  snakes,  the  teeth  are  only  used  to  hold 
the  prey,  and  not  for  mastication ;  and  in  others,  such  as  the 
turtles  and  birds,  the  jaws  are  not  furnished  with  any  teeth 
at  all.  The  food  is  also  usually  subjected  in  the  mouth  to  the 
action  of  a  special  fluid — the  saliva — which  acts  chemically  as 
well  as  mechanically  upon  the  food,  and  which  is  secreted  by 
special  glands,  known  as  the  "  salivary  glands."  From  the 
mouth  the  food  passes  through  a  muscular  tube — the  gullet, 
or  oesophagus  (Fig.  98,  g) — to  the  proper  digestive  cavity,  or 
stomach  (s).  Here  it  is  subjected  to  the  action  of  a  special 
digestive  fluid — the  "  gastric  juice  " — and  is  converted  into  a 
thick,  pasty  fluid,  which  is  called  chyme.  From  the  stomach 
the  chyme  passes  into  a  long,  convoluted,  muscular  tube,  which 


202 


VERTEBRATE  ANIMALS. 


is  called  the  "  small  intestine  "  (sm).  Here  it  is  subjected  to 
the  action  of  two  other  digestive  fluids,  called  the  "  bile  "  and 
"  pancreatic  juice,"  as  well  as  to  the  fluids  secreted  by  the 
intestine  itself.  The  bile  is  secreted  by  a  large  gland,  which 
is  known  as  the  "  liver,"  while  the  pancreatic  juice  is  produced 
by  another,  termed  the  "  pancreas,"  both  pouring  their  secre- 
tion into  the  upper  part  of  the  small 
intestine.  By  the  combined  action 
of  these  digestive  fluids  the  chyme 
is  ultimately  converted  into  a  milky 
fluid,  which  is  called  chyle,  when  it 
is  fit  to  be  taken  up  into  the  blood- 
vessels. The  small  intestine  finally 
opens  into  a  tube  of  larger  diameter, 
which  is  called  the  "  large  intestine  " 
(Zm),  and  this  opens  on  the  surface 
of  the  body  by  an  anal  aperture.  In 
the  large  intestine  the  last  remain- 
ing portions  of  the  food  which  can 
be  rendered  useful  are  absorbed  into 
the  blood,  the  indigestible  portions 
being  ultimately  got  rid  of  as  use- 
less. The  fluid  products  of  diges- 
tion (chyle)  are  chiefly  absorbed 
from  the  intestinal  canal  by  a  set  of 
special  vessels,  which  are  present  in 
all  Vertebrates,  and  which  are  called 
the  lacteals  (Lat.  lac,  milk)  from  the 
milky  fluid  they  contain.  These 
lacteals  combine  to  form  a  large 
.  *^  by  which  their  contents  are 
Small  in-  ultimately  added  to  the  circulating 
£<£  Wood.  Part  of  the  products  of  di- 
final  ^portion,  called  the  "rec-  gestion  are  absorbed  by  the  veins 
which  ramify  on  the  intestinal  canal, 

and  which  ultimately  unite  to  form  a  great  vessel,  called  the 
"  vena  portse,"  which  goes  to  the  liver.  The  materials,  how- 
ever, which  are  taken  up  in  this  way  also  ultimately  reach  the 
circulating  blood.  In  this  way,  therefore,  fresh  matter  is 
being  constantly  added  to  the  blood  to  replace  the  waste 
caused  by  the  performance  of  the  vital  functions. 

The  blood  is  thus  formed  out  of  the  materials  which  are 
taken  into  the  alimentary  canal  as  food ;  and  in  all  the  Verte- 
brata  (with  one  exception)  it  is  of  a  red  color,  when  viewed  in 


GENERAL   CHARACTERS   OF  THE  VERTEBRATA.        203 

mass.  This  is  due  to  the  presence  in  it  of  numerous  micro- 
scopical particles,  which  are  known  as  the  "  blood-corpuscles," 
the  fluid  itself  being  colorless.  In  Fig.  99  are  represented 


FIG.  99.— Blood-corpuscles,  magnified,    a  Man ;  &  Goose;  c  Crocodile;  d  Frog;  e  Skate. 

some  of  the  forms  of  blood-corpuscles  which  are  found  in  dif- 
ferent divisions  of  the  Vertebrata. 

The  blood  is  always  distributed  through  the  body  by 
means  of  a  system  of  closed  tubes,  which  constitute  the  "blood- 
vessels," and,  with  the  single  exception  of  the  Lancelet,  it  is 
always  propelled  by  means  of  a  contractile  muscular  cavity  or 
"  heart."  The  heart  and  other  circulatory  arrangements  differ 
considerably  in  different  classes  of  the  Vertebrata,  but  these 
differences  will  be  best  considered  at  a  later  period.  Respira- 
tion in  all  the  Vertebrata  is  effected  by  means  of  distinct 
breathing-organs,  assisted  in  many  cases  by  the  skin.  In  the 
water-breathing  Vertebrates,  such  as  fishes,  the  respiratory 
organs  are  in  the  form  of  gills  or  branchiae,  which  are  richly 
supplied  with  blood,  and  are  exposed  to  the  influence  of  water 
holding  oxygen  in  solution.  In  the  air-breathing  Vertebrates, 
the  breathing  organs  are  in  the  form  of  lungs.  These  essen- 
tially consist  of  cellular  or  spongy  organs,  placed  in  the  cavity 
of  the  chest,  richly  furnished  with  blood-vessels,  and  receiving 
constant  supplies  of  fresh  air  by  means  of  a  tube  which  opens 
in  the  throat  and  is  known  as  the  "  windpipe,"  or  trachea.  In 
the  higher  Vertebrates  the  heart  becomes  a  double  organ,  one 
side  being  concerned  wholly  with  driving  the  impure  (venous) 
blood  to  the  lungs,  while  the  other  side  propels  the  pure  oxy- 
genated (arterial]  blood  to  all  parts  of  the  body. 

The  waste  substances  of  the  body — of  which  the  most  im- 
portant are  water,  carbonic  acid,  and  the  peculiar  substance 
called  urea — are  got  rid  of  by  the  skin  and  lungs,  but  prin- 
cipally by  two  glands  which  are  called  the  kidneys.  The  ex- 
cretion of  urea  from  the  body,  as  a  general  rule,  is  wholly 
effected  by  means  of  the  kidneys  alone ;  and  this  is  their  most 
important  function,  as  the  retention  of  this  substance  within 
the  body  rapidly  causes  death.  The  secretion  of  the  kidneys 
is  sometimes  got  rid  of  by  means  of  special  canals  appropriated 


204  VERTEBRATE  ANIMALS. 

to  this  alone ;  but  in  the  lower  Vertebrata  it  is  discharged  in- 
to the  hinder  extremity  of  the  alimentary  canal,  and  is  evacu- 
ated along  with  the  undigested  portions  of  the  food. 

The  nervous  system  varies  greatly  in  its  development  in 
the  Vertebrata.  In  the  little  fish  called  the  Lancelet,  the  main 
mass  of  the  nervous  system  consists  of  a  cord  of  nervous  mat- 
ter, representing  the  spinal  marrow,  but  not  having  in  front 
any  enlargement  which  represents  the  brain.  In  all  the  other 
Vertebrata  the  central  masses  of  the  nervous  system  (termed 
the  cerebro-spinal  axis)  consist  of  a  nervous  cord  (the  spinal 
cord)  contained  in  the  canal  formed  by  the  neural  arches  of 
the  vertebrae,  and  of  an  anterior  mass  of  nervous  matter,  which 
is  protected  by  the  skull,  and  is  termed  the  encephalon  or 
brain.  The  size  and  development,  however,  of  the  brain  vary 
enormously  in  different  Vertebrates ;  and  in  the  lower  forms 
the  brain  is  little  more  than  an  aggregation  or  collection  of 
nervous  masses  or  "  ganglia,"  which  are  connected  with  the 
special  senses,  sight,  hearing,  taste,  and  smell,  special  organs 
for  which  are  present  in  almost  all  the  Vertebrata. 

Reproduction  in  the  Vertebrata  is  always  truly  sexual,  the 
sexes  are  always  in  different  individuals,  and  in  no  case  are 
compound  organisms  produced  by  a  process  of  budding  or  fis- 
sion. Most  are  oviparous,  producing  eggs  from  which  the 
young  are  developed.  Some  retain  the  eggs  within  the  body 
till  the  young  are  ready  to  be  hatched,  and  these  are  some- 
times said  to  be  ovo-viviparous.  The  higher  Vertebrates, 
however,  bring  forth  their  young  alive,  and  are  said  to  be 
viviparous  (Latin,  vivus,  living ;  and  pario,  I  bring  forth). 

PRIMARY  DIVISIONS  OF  THE  VEBTEBRATA.  —  The  Verte- 
brata are  variously  divided  into  great  primary  sections  b}T  dif- 
ferent writers,  and  all  of  these  divisions  have  more  or  less 
merit.  Here,  however,  the  classification  proposed  by  Prof. 
Huxley  will  be  followed,  and  it  is  not  necessary  to  enter  into 
any  consideration  of  the  others.  It  has  also  been  thought  ad- 
visable to  give  in  this  place  a  brief  account  of  the  leading 
characters  which  separate  these  divisions  from  one  another, 
though  it  is  not  to  be  expected  that  the  learner  will  be  able 
to  appreciate  the  full  value  of  these  characters  till  he  has  com- 
pleted his  study  of  the  Vertebrata  as  a  whole. 

The  Vertebrata  are  divided  by  Prof.  Huxley  into  the  fol- 
lowing great  divisions : 

I.  ICHTHYOPSIDA  (Gr.  ichtfius,  a  fish;  and  opsis,  appear- 
ance).— In  this  section  are  included  the  fishes  (Class  Pisces), 


GENERAL  CHARACTERS   OF  THE  VERTEBRATA.        205 

and  the  frogs,  newts,  and  their  allies  (Class  Amphibia).  They 
are  all  characterized  by  the  fact  that  they  possess  gills  or 
branchiae,  either  throughout  life  or  during  the  earlier  stages 
of  their  existence ;  that  they  possess  nucleated  red  blood- 
corpuscles  (i.  e.,  blood-corpuscles  with  a  central  particle  or 
nucleus.  Fig.  99,  d,  e),  and  by  certain  embryonic  characters  as 
well.  From  the  temporary  or  permanent  possession  of  gills, 
they  are  often  spoken  of  as  the  Branchiate  Vertebrates. 

II.  SAUROPSIDA  (Gr.  saura,  a  lizard;  and  opsis,  appear- 
ance).— In  this  division  are  the  birds  (Class  Aves),  and  the 
true  reptiles  (Class  Reptilia).     They  are  characterized  by  the 
fact  that  at  no  time  of  their  life  are  they  ever  provided  with 
gills ;  that  the  skull  is  jointed  to  the  vertebral  column  by  a 
single  articulating  surface  (or  condyle) ;  that  the  lower  jaw  is 
composed  of  several  pieces,  and  is  united  to  the  skull  by 
means  of  a  special  bone  (called  the  os  quadratum] ;  that  they 
possess  nucleated  red  blood-corpuscles  (Fig.  99,  #,  c\  and  by 
certain  embryonic  characters  as  well.* 

III.  MAMMALIA   (Lat.   mamma,  the  breast). — In  this  di- 
vision are  all  the  ordinary  quadrupeds ;  characterized  by  the 
constant  absence  of  gills;  by  the  skull  being  jointed  to  the 
vertebral  column  by  two  articulating  surfaces  (or  condyles) ; 
by  the  fact  that  the  lower  jaw  is  composed  of  only  two  pieces, 
and  is  not  united  to  the  skull  by  means  of  a  special  bone  (the 
quadrate  bone) ;  by  having  non-nucleated  red  blood-corpuscles 
(Fig.  99,  a) ;  and  by  having  special  glands  —  the  mammary 
glands — which  secrete  a  special   fluid — the  milk — by  which 
the  young  are  nourished  for  a  longer  or  shorter  period  after 
birth. 

These   three   primary    divisions   comprise   the   five   great 
classes  into  which  the  Vertebrata  are  divided : 

1.  Fishes  (Pisces). 

2.  Amphibia  (Frogs,  Newts,  etc.). 

3.  Heptilia  (True  Reptiles). 

4.  Aves  (Birds). 

5.  Mammalia. 

*  Recent  researches  have  led  to  the  belief  that  the  appearance  of  nuclei  in  the  red  blood- 
corpuscles  of  the  Oviparous  Vertebrates  is  due  to  changes  taking  place  after  death,  and  that 
these  structures  are  not  present  during  life. 

10 


ICHTHYOPSIDA. 

CHAPTER  XXIV. 
CLASS  I.  PISCES. 

THE  fishes  form  the  lowest  class  of  the  Vertebrata,  and 
they  may  be  broadly  defined  as  being  Vertebrate  animals  pro- 
vided with  gills,  whereby  they  are  enabled  to  breathe  air  dis- 
solved in  water ;  the  heart,  when  present,  consists  of  a  single 
auricle  and  ventricle  (with  the  exception  of  the  mud-fishes)  ; 
and  the  limbs,  when  present,  are  in  the  form  of  fins,  or  expan- 
sions of  the  integument. 

In  their  external  form,  fishes  are  in  most  cases  adapted  for 
rapid  locomotion  in  water,  the  shape  of  the  body  being  such 
as  to  cause  the  least  possible  friction  in  swimming.  To  this 
end,  as  well  as  for  purposes  of  defence,  the  body  is  generally 
enveloped  in  a  species  of  chain-mail  formed  by  overlapping 
scales,  to  which  bony  plates,  tubercles,  and  spines,  are  some- 
times added.  Valuable  characters  can  sometimes  be  drawn 
from  the  nature  of  the  scales,  and  with  a  view  to  this  the 
integumentary  appendages  of  fishes  have  been  divided  by 
Agassiz  as  follows  (Fig.  100) : 

1.  Cycloid  scales  (a),  consisting  of  thin,  flexible,  horny 
scales,  which  are  circular  or  elliptical  in  shape,  and  have  a 
smooth  outline.     These  scales  occur  in  most  of  our  common 
fishes  (e.  g.,  the  pike). 

2.  Ctenoid  scales  (b).     These  resemble  the  cycloid  scales 
in  being  thin,  flexible,  horny  scales,  but  they  are  distinguished 
by  having  their  hinder  margins  cut  into  comb-like  projections, 
or  fringed  with  spines.     The  common  perch  supplies  a  good 
example  of  these  scales. 

3.  Placoid  scales  (c).     These  are  detached  bony  grains, 


PISCES. 


207 


tubercles,  or  plates,  scattered  through  the  skin,  and  sometimes 
armed  with  projecting  spines. 

4.  Ganoid  scales  (</,)  composed  of  a  layer  of  true  bone, 
covered  by  a  layer  of  hard  polished  enamel.  These  scales  are 
usually  much  thicker  and  larger  than  the  ordinary  scales ;  they 
are  often  oblong  or  rhomboidal  in  shape ;  they  are  often  con- 
nected together  by  little  processes ; 
and  they  generally  are  in  contact  by 
their  edges,  but  rarely  overlap  one 
another.  In  most  fishes  there  is 
also  to  be  observed  a  line  of  peculiar 
scales,  forming  what  is  called  the 
"lateral  line."  Each  of  the  scales 
of  this  line  is  perforated  by  a  minute 
tube,  which  leads  into  a  longitudinal 
canal,  believed  to  secrete  the  mucus 
with  which  the  general  surface  is 
lubricated,  or  to  have  some  sensory 
function. 

As  regards  the  true  internal 
skeleton,  fishes  differ  very  widely 
from  one  another,  but  the  skeleton  T 

,..,',  ,.  -     FIG.  100.— Scales  of  different  Fishes. 

is  so  complicated  that  only  a  lew  of 
the  most  important  points  can  be 
mentioned  here.  In  one  fish — the 
Lancelet — there  can  hardly  be  said 

to  be  any  true  skeleton,  the  vertebral  column  being  repre- 
sented permanently  by  the  semi-gelatinous  notochord  (Fig. 
105).  In  others,  such  as  the  Lampreys,  Sturgeons,  and  Rays, 
the  skeleton  remains  permanently  in  the  condition  of  gristle 
(cartilage)  ;  in  others  it  is  partially  cartilaginous  and  partially 
ossified ;  and,  lastly,  in  most  modern  fishes,  it  is  completely 
converted  into  bone.  The  vertebral  column  in  a  bony  fish 
consists  of  a  number  of  vertebrae  which  are  hollow  or  cup- 
shaped  at  both  ends  (bi-concave  or  "  amphiccelous  "),  the  cup- 
like  margins  being  united  together  by  ligaments.  The  cavities 
formed  by  the  apposition  of  the  vertebrae  are  filled  with  the 
gelatinous  remains  of  the  notochord.  This  gelatinous  elastic 
substance  acts  as  a  ball-and-socket  joint  between  the  vertebrae, 
thus  giving  the  whole  spine  the  extreme  flexibility  which  is 
essential  to  animals  living  in  a  watery  medium.  The  entire 
spinal  column  is  divisible  into  no  more  than  two  distinct 
regions,  an  abdominal  and  a  caudal.  The  ribs  are  attached 
to  the  transverse  processes  or  to  the  bodies  of  the  abdominal 


a  Cycloid  scale  (Pike) ;  6  Ctenoid 
scale  (Perch);  c  Placoid  scale 
(Thornback) ;  d  Ganoid  scale  (Pa- 
IcEoniscus). 


208 


VERTEBRATE  ANIMALS. 


vertebras  (Fig.  101,  r)  ;  and  they  do  not  enclose  any  thoracic 
cavity,  or  protect  the  organs  which  are  usually  contained  in 
the  chest  —  namely,  the  heart  and  breathing-organs.  The 
anterior  or  lower  ends  of  the  ribs  of  fishes  are  free,  or  are 
rarely  united  to  hard  productions  of  the  integument ;  but  there 
is  never  any  breastbone  or  sternum  properly  so  called. 


FIG.  101.— Skeleton  of  the  common  Perch  (Percafluviatilis).    p  Pectoral  fin;  v  One  of  tho 
ventral  fii 
dorsal  fin ; 
bones; 

The  only  remaining  bones  of  the  trunk  proper  are  the  so- 
called  "  interspinous  bones  "  (Fig.  101,  i  i}.  These  are  a  series 
of  pointed,  dagger-like  bones,  imbedded  in  the  middle  line  of 
the  body,  between  the  great  lateral  muscles  which  form  the 
greater  part  of  the  body  of  a  fish.  The  inner  ends  or  points 
of  the  interspinous  bones  are  attached  by  ligament  to  the 
spinous  processes  of  the  vertebras,  and  at  their  outer  ends  they 
support  the  framework  (rays)  of  the  so-called  "  median  "  fins. 
As  a  rule  there  is  only  one  interspinous  bone  to  each  vertebra, 
but  in  the  flat-fishes  (Sole,  Turbot,  etc.)  there  are  two.  The 
limbs  of  fishes  may  be  wholly  wanting,  or  one  pair  may  be  ab- 
sent, but  in  no  case  is  the  number  greater  than  the  regular 
vertebrate  type — namely,  two  pairs.  When  developed,  how- 
ever, the  limbs  of  fishes  are  very  different  from  those  of  other 
Vertebrates,  consisting  of  expansions  of  the  integument, 
furnished  with  bony  or  gristly  supports  or  rays,  and  thus  con- 
stituting what  are  called  "fins"  (Fig.  102).  The  pair  of  limbs 
which  correspond  to  the  arms  of  man  and  to  the  fore-limbs  of 
other  Vertebrates  are  termed  the  pectoral  fins,  and  they  are 


PISCES.  209 


attached  to  a  bony  arch  which  is  attached  either  to  the  back 
of  the  skull  or  to  the  spinal  column  (Fig.  101,  p,  and  102,  p). 
The  hind-limbs  in  fishes  are  known  as  the  ventral  fins  (Figs. 
101,  102,  v),  and  are  not  only  often  wanting  altogether,  but 
when  present  are  less  developed  than  the  pectorals  and  less 
fixed  in  their  position.  They  are  united  to  an  imperfect  bony 


FIG.  102. — Outline  of  a  Fish  (Perca  granulata),  showing1  the  "paired"  and  "median"  fins. 
p  Pectoral  fin ;  v  Ventral  fin ;  d  First  dorsal  fin ;  d'  Second  dorsal  fin ;  c  Caudal  fin ; 
a  Anal  fin. 


arch,  which  represents  the  innominate  bones,  or  pelvic  arch, 
of  the  higher  Vertebrates,  but  which  is  never  joined  to  the 
spinal  column.  In  some  fishes  the  ventral  fins  are  placed  far 
back,  and  in  these  the  bony  arch  which  supports  them  is  freely 
suspended  in  the  muscles.  In  others  the  ventral  fins  are  alto- 
gether out  of  position,  and  are  placed  beneath,  or  even  in 
front  of  the  pectoral  fins ;  and  in  these  cases  the  pelvic  arch  is 
attached  to  part  of  the  pectoral  arch.  The  pectoral  and  ven- 
tral fins  represent,  as  just  said,  the  fore  and  hind  limbs,  and 
consequently  there  are  always  two  of  each,  when  they  are 
present  at  all.  They  are,  therefore,  spoken  of  as  the  "  paired  " 
fins.  Besides  these,  however,  or  in  the  absence  of  one  or 
other  of  these,  there  is  also  a  series  of  what  are  called  "  me- 
dian "  fins ;  that  is  to  say,  fins  which  are  placed  in  the  middle 
line  of  the  body,  and  which  are  unpaired,  having  no  fellows. 
These  median  fins  agree  with  the  paired  fins  in  being  expan- 
sions of  the  integument,  supported  by  bony  or  gristly  supports 
or  "  rays,"  and  they  are  carried  by  the  heads  of  the  "  inter- 
spinous"  bones,  already  described  (Fig.  101,  if).  They  are 


210 


VERTEBRATE  ANIMALS. 


a  Homocercal  tail  (Sword-fish) ;  b 
Heterocercal  tail  (Sturgeon). 


Variable  in  number,  and  in  some  cases  there  is  only  a  single 

fringe  running  round  the  hinder 
extremity  of  the  body.  Common- 
ly, however,  the  median  fins  con- 
sist of  one  or  two  expansions  of 
the  dorsal  integument,  called  the 
"dorsal"  fins  (Fig.  101,  d  d')  ;  one 
or  two  on  the  ventral  or  lower 
surface  near  the  vent,  called  the 
"  anal "  fins  (a)  ;  and  a  broad  fin 
at  the  extremity  of  the  vertebral 
column,  constituting  ihe  "  caudal " 
fin  or  tail  (c). 

The  tail  in  all  fishes  is  placed 
vertically — that  is  to  say,  it  strikes 
the  water  laterally,  or  from  side  to 
side,  and  it  is  the  chief  organ  of 

FIG.  103.— Tails  of  different  Fishes,   progression  in  the  fish.    Two  very 

distinct  types  of  tail  are  found 
among  the  fishes.  In  one  of  these, 
found  in  most  living  forms,  the  tail  is  composed  of  two  nearly 
equal  lobes  which  spring  from  the  end  of  the  spine  (Fig.  103, 
a).  This  form  of  tail  is  said  to  be  "homocercal."  In  the 
other  type  of  tail,  found  in  the  dog-fishes,  sharks,  and  other 
living  fishes,  as  well  as  in  many  extinct  forms,  the  tail  is  un- 
equally lobed,  and  is  said  to  be  "  heterocercal "  (Fig.  103,  I). 
In  these  forms  the  vertebral  column  is  prolonged  into  the 
upper  lobe  of  the  tail,  and  the  greater  portion  of  the  tail  is 
found  below  the  spine. 

In  both  the  paired  and  the  median  fins  the  integument  is 
supported  by  a  series  of  spine-like  bones,  which  are  called 
"  rays."  These  rays  are  sometimes  simple  undivided  rays  or 
spines,  when  they  are  called  "  spinous  rays  "  (Fig.  101,  d) ;  but 
in  other  cases  they  are  both  divided  by  transverse  joints,  and 
split  up  into  numerous  longitudinal  branches  toward  their  ex- 
tremities, when  they  are  spoken  of  as  "  soft  rays  "  (Fig.  101, 
d').  The  soft  rays  occur  in  many  fishes  in  different  fins,  but 
they  are  invariably  present  in  the  caudal  fin  or  tail. 

As  regards  the  digestive  system  in  fishes,  the  mouth  is 
Usually  furnished  with  a  complicated  system  of  teeth,  de- 
veloped not  only  upon  the  jaws,  but  upon  any  or  every  bone 
which  enters  into  the  composition  of  the  oral  cavity.  The 
gullet  opens  into  a  stomach,  usually  of  large  size,  and  its  hin- 
der aperture  (the  pylorus)  is  usually  furnished  with  a  valve. 


PISCES.  211 

Immediately  behind  the  pyloric  opening  of  the  stomach  there 
is  usually  a  variable  number  of  blind  tubes  (called  the  "  py- 
loric caeca  ")  which  open  into  the  intestine,  and  which  are  be- 
lieved to  represent  the  pancreas.  In  some  fishes,  however, 
there  is  a  well-developed  pancreas,  and  in  others  even  these 
tubes  are  wanting.  The  intestinal  canal  is  a  longer  or  shorter, 
more  or  less  convoluted  tube,  and  its  absorbing  surface  is 
sometimes  largely  increased  by  a  spiral  folding  of  the  mucous 
membrane,  which  winds  like  a  screw  in  close  turns  from  the 
pylorus  to  the  anus.  The  liver  is  usually  of  large  size,  and 
saturated  with  oil,  but  in  the  Lancelet  it  is  doubtfully  rep- 
resented by  a  hollow,  sac-like  organ.  The  kidneys  in  fishes 
are  of  great  comparative  size,  forming  two  elongated  organs, 
situated  beneath  the  spine,  and  extending  along  the  whole 
length  of  the  abdomen. 

Respiration  in  all  fishes  is  aquatic,  and  is  effected  by  means 
of  gills  or  branchiae,  in  all  except  the  Lancelet,  in  which  res- 
piration is  effected  by  branchial  filaments  placed  round  the 
pharynx,  and  also  by  a  greatly-developed  pharynx  perforated 
*>y  ciliated  apertures  (Fig.  105).  The  arrangement  and  struct- 
.re  of  the  gills  in  fishes  vary  a  good  deal  in  different  orders, 
and  the  leading  modifications  will  be  noticed  hereafter.  In 
the  mean  while  it  will  be  sufficient  to  give  a  short  description 
of  the  branchial  apparatus  in  one  of  the  bony  fishes.  In  such 
a  fish  the  gills  consist  of  a  single  or  double  series  of  flat  carti- 
laginous leaflets,  covered  by  mucous  membrane,  richly  supplied 
with  blood,  and  arranged  on  bony  or  cartilaginous  arches 
which  are  connected  with  the  tongue-bone  (hyoid  bone)  below 
and  with  the  under  surface  of  the  head  above.  The  branchial 
arches  and  branchias  are  suspended  in  cavities  placed  on  the 
side  of  the  neck,  and  in  the  ordinary  bony  fishes  there  is  only 
one  such  cavity  on  each  side.  The  water  is  taken  in  at  the 
mouth  by  a  process  analogous  to  swallowing,  and  it  gains  ad- 
mission to  the  branchial  chamber  by  means  of  a  series  of  clefts 
or  slits  which  perforate  the  sides  of  the  pharynx.  Having 
passed  over  the  gills  and  lost  its  oxygen,  the  effete  water 
makes  its  escape  behind  by  an  aperture  called  the  "  gill-slit," 
which  is  placed  on  the  side  of  the  neck.  The  opening  of  the 
gill-slit  is  closed  in  front  by  a  chain  of  flat  bones  which  con- 
stitute the  "  gill-cover,"  and  by  a  membrane  which  is  sup- 
ported upon  a  variable  number  of  slender  bony  spines.  This 
is  the  general  mechanism  of  respiration  in  one  of  the  bony 
fishes,  but  different  arrangements  are  found  in  other  cases, 
which  will  be  subsequently  noticed. 


212 


VERTEBRATE  ANIMALS. 


The  heart  in  fishes  may  be  regarded  as  essentially  a 
branchial  or  respiratory  heart,  being  concerned  chiefly  with 
driving  the  venous  and  impure  blood  to  the  gills.  It  con- 
sists in  almost  all  cases  of  two 
cavities,  an  auricle  and  a  ventricle 
(Fig.  104).  The  auricle  (a)  receives 
the  venous  blood  which  has  passed 
through  all  the  various  parts  of  the 
body,  and  propels  it  into  the  ven- 
tricle (v).  From  the  ventricle  pro- 
ceeds a  single  great  vessel  (the 
"branchial  artery"),  the  base  of 
which  is  usually  developed  into  a 
muscular  cavity,  the  "bulbus  arte- 
riosus"  (m),  which  acts  as  a  kind  of 
additional  ventricle.  By  the  ventri- 
cle and  bulbus  arteriosus  the  venous 
blood  is  driven  to  the  gills,  where  it 
is  subjected  to  the  action  of  the  wa- 
ter. The  aerated  blood  is  not  re- 
turned to  the  heart,  but  is  driven 
from  the  gills  through  all  parts  of 
the  body,  the  propulsive  force  neces- 
sary for  this  being  derived  partly 
from  the  heart,  and  partly  from  the 
contractions  of  the  muscles  between 
which  the  blood-vessels  pass.  The 
FIG.  104.—  Diagram  of  the  circuia-  essential  peculiarity  of  the  circulation 
fi*  *!&&SS?1E;  of  fishes  consists  in  this,  that  the  ar- 
venous  system  is  left  light.  aAu-  terialized  blood  returned  from  the 

ricle,  receiving  the  venous  blood       „.  ,,     ..      ..  ,        , 

from  the  body;  «  Ventricle;  m    gills    IS   propelled    through    the    gen- 

Bulbus  arteriosus;   n  Branchial  i    Trac«^la     rvf    +1-,^    Korlv    /cTrcf^rmV 


Korl 

artery,  carrying  the  venous  blood  DOd 

to  the  gills  (&);  c  Great  systemic  vessels)  without  being  sent  back  to 

vessel,  carrying  the  pure  blood    ,11,          T      j/i         f  i    ^        i 

to  the  tissues.  the  heart.      In  the   JLancelet,  alone 

of  all  fishes,  there  is  no  single  heart, 

and  the  circulation  is  effected  by  means  of  contractile  dila- 
tations situated  upon  several  of  the  vessels.  In  the  Mud- 
fish (Lepidosiren)  the  heart  consists  of  two  auricles  and  a 
ventricle.  In  all  cases  the  blood  is  cold,  or,  in  other  words, 
has  a  temperature  very  little,  or  not  at  all,  higher  than  that 
of  the  surrounding  medium.  The  blood-corpuscles  (Fig.  99, 
e)  are  always  nucleated,  and,  except  in  the  Lancelet,  are 
most  of  them  red. 

While  the  respiration  of  all  fishes  is  truly  aquatic,  most 


PISCES.  OJ3 

are,  nevertheless,  furnished  with  an  organ  which  doubtless 
corresponds  to  (or  is  homologous  with)  the  lungs  of  the  higher 
Vertebrata.  This  is  known  as  the  "  air  "  or  "  swim  bladder," 
and  is  a  sac  filled  with  gas  and  situated  between  the  alimen- 
tary canal  and  the  kidneys.  In  most  cases,  the  sac  contains 
only  a  single  cavity,  but,  in  many  instances,  it  is  variously 
divided  by  partitions.  In  most  fresh-water  fishes,  the  gases  in 
the  swim-bladder  are  mainly  composed  of  nitrogen,  but,  in  the 
sea  fishes,  it  is  chiefly  filled  with  oxygen.  The  sac  of  the 
swim-bladder  is  often  closed,  but,  in  other  cases,  it  opens  into 
the  gullet  by  means  of  a  duct  which  corresponds  to  the  wind- 
pipe. In  the  great  majority  of  fishes,  the  functions  of  the 
air-bladder  are  mainly  hydrostatic,  that  is  to  say,  it  serves  to 
maintain  the  necessary  agreement  between  the  specific  gravity 
of  the  fish  and  that  of  the  surrounding  water.  In  the  singu- 
lar Mud-fish  (Lepidosiren),  the  air-bladder  is  composed  of  two 
distinct  sacs,  divided  into  a  number  of  cellular  compartments, 
and  opening  into  the  gullet  by  a  tube.  In  this  fish  it  acts  as 
a  respiratory  organ,  and  is,  therefore,  not  only  in  structure,  but 
also  in  function,  the  representative  of  the  lungs  of  the  other 
Vertebrates. 

The  nervous  system  of  fishes  is  of  an  inferior  type  of  or- 
ganization, the  brain  being  of  comparatively  small  size,  and 
consisting  mainly  of  a  collection  of  ganglia.  As  regards  the  or- 
gans of  the  senses,  two  peculiarities  deserve  notice.  In  the  first 
place,  though  fishes  possess  the  essential  parts  of  the  organ 
of  hearing,  they  possess  no  external  ears,  and  in  no  -case  is 
there  any  direct  communication  between  the  ear  and  the  outer 
world.  In  the  second  place,  the  organs  of  smell  consist  of  a 
double  cavity  lined  by  a  mucous  membrane  folded  into  numer- 
ous plaits,  into  which  water  is  admitted,  usually  by  two  dis- 
tinct apertures  or  nostrils.  Behind,  however,  the  nasal  sacs 
are  closed,  and  they  do  not  communicate  by  any  aperture  with 
the  throat,  as  they  do  in  all  the  higher  Vertebrates.  The  only 
exceptions  to  this  rule  are  the  Hag-fishes  and  their  allies 
(Myxinoids)  and  the  Mud-fish  (Lepidosiren). 

As  regards  their  reproductive  system,  most  fishes  are  truly 
oviparous,  and  the  ovaries  are  familiarly  known  as  the  "  roe." 
Some  fishes  are  ovo-viviparous,  retaining  their  eggs  within  the 
body  till  the  young  are  hatched.  The  male  organs  of  repro- 
duction are  commonly  spoken  of  as  the  "  milt "  or  "  soft  roe." 


CHAPTER  XXV. 

OEDEES     OF     FISHES. 

THE  number  of  different  kinds  of  fishes  is  so  enormous  that 
nothing  further  will  be  attempted  than  merely  to  give  an  out- 
line of  the  leading  peculiarities  which  distinguish  the  different 
orders.  The  classification  here  adopted  is  the  one  proposed 
by  Prof.  Huxley,  who  divides  the  class  Pisces  into  the  follow- 
ing six  orders : 

1.  Pharyngobranchii. 

2.  Marsipobranchii. 

3.  Teleostei. 

4.  Ganoidei. 

5.  ElasmobranchiL 

6.  Dipnoi. 

OEDEE  I.  PHAEYNGOBEAKCHII  (Gr.  pliarugx,  the  upper  part 
of  the  gullet,  and  bragchia,  gills). — This  order  of  fishes  in- 
cludes only  a  single  animal,  the  anomalous  Amphioxus,  or 
Lancelot,  the  organization  of  which  differs  in  almost  all  its 
important  points  from  that  of  all  the  other  members  of  the 
class.  In  fact,  the  Lancelet  presents  us  with  the  lowest  type 
of  organization  as  yet  known  in  the  Vertebrata.  The  Lance- 
let  is  an  extraordinary  little  fish,  from  one  and  a  half  to  two 
inches  long,  which  burrows  in  sand-banks  in  various  seas,  but 
is  especially  abundant  in  the  Mediterranean.  The  body  is 
lanceolate  in  shape,  and  is  provided  with  a  narrow  membra- 
nous border,  of  the  nature  of  a  median  fin,  which  runs  along 
the  whole  of  the  dorsal  and  a  portion  of  the  ventral  surface, 
and  expands  at  the  tail  to  form  a  lancet-shaped  caudal  fin. 
There  are  no  true  "  paired "  fins,  representing  the  fore  and 
hind  limbs.  The  mouth  is  a  longitudinal  fissure,  placed  at  the 
front  of  the  head,  and  completely  destitute  of  jaws,  but  sur- 


ORDERS  OF  FISHES. 


215 


rounded  by  a  number  of  cartilaginous  filaments.  The  throat 
is  provided  with  several  leaf-like  filaments,  which  are  richly 
supplied  with  blood,  and  are  believed  to  discharge  in  part  the 
function  of  gills.  The  mouth  (Fig.  105,  m)  opens  into  a 
dilated  chamber,  which  is  believed  to  represent  the  pharynx, 
and  is  termed  the  pharyngeal  or  "  branchial "  sac.  The  walls 
of  this  chamber  (p)  are  strengthened  by  numerous  cartilagi- 


FIG.  105. — Diagram  of  the  Lancelet  (AmpMoxus  lanceolatus).  m  Mouth  with  cartilagi- 
nous filaments  ;  p  Greatly-developed  pharynx,  or  branchial  sac,  perforated  by  ciliated 
apertures;  i  Intestine;  a  Anus;  h  Blood-vessels,  with  pulsating  dilatations  in  place 
of  a  heart ;  ch  Notochord ;  n  Spinal  cord. 

nous  filaments,  between  which  are  a  series  of  transverse  slits 
or  clefts,  and  the  whole  is  covered  with  a  richly-ciliated  mu- 
cous membrane.  The  function  of  this  sac  is  clearly  respiratory, 
the  water  from  without  being  admitted  through  the  mouth, 
passing  through  the  branchial  clefts  into  the  abdominal  cavity, 
and  finally  escaping  by  means  of  an  aperture  placed  on  the 
ventral  surface  a  little  in  front  of  the  anus.  From  the  hinder 
end  of  the  branchial  sac  proceeds  the  alimentary  canal,  which 
has  appended  to  it  a  sac-like  organ,  believed  to  represent  the 
liver,  and  which  terminates  behind  in  a  distinct  anal  aperture. 
There  is  no  heart,  and  the  circulation  is  entirely  effected  by 
means  of  several  contractile  dilatations,  developed  upon  the 
great  blood-vessels  (h).  The  blood  itself  is  colorless.  No 
kidneys  have  hitherto  been  discovered,  and  the  reproductive 
elements  are  emitted  into  the  abdominal  cavity,  from  which 
they  escape  by  the  pore  placed  upon  the  lower  surface. 

There  is  no  skeleton  properly  so  called.  The  notochord 
(ch)  remains  throughout  life  as  a  semi-gelatinous  rod,  enclosed 
in  a  membranous  sheath,  and  supporting  the  spinal  cord. 
There  is  no  skull,  and  the  spinal  cord  (n)  does  not  expand  in 
front  to  form  a  distinct  brain.  The  brain,  however,  may  be 
said  to  be  represented,  as  the  front  portion  of  the  nervous 
axis  gives  off  nerves  to  a  pair  of  eyes,  and  another  branch  to 


216  VERTEBRATE  ANIMALS. 

a  ciliated  pit,  which  is  believed  to  be  a  rudimentary  organ  of 
smell. 

OEDEK  II.  MARSIPOBEANCHII  (Gr.  marsipos,  a  pouch ;  brag- 
chia,  gills). — This  order  includes  the  Hag-fishes  (Myxinidce) 
and  the  Lampreys  (PetromyzonidvB),  and  it  is  defined  by  the 
following  characters :  The  body  is  cylindrical  and  worm-like, 
and  is  destitute  of  limbs.  The  skull  is  cartilaginous,  there  is 
no  lower  jaw,  and  the  notochord  remains  through  life,  so  that 
there  is  no  vertebral  column.  The  heart  is  composed  of  an 
auricle  and  a  ventricle,  but  there  is  no  bulbus  arteriosus.  The 
gills  are  pouch-like,  communicating  with  the  throat  on  the 
one  hand,  and  opening  externally  on  the  other  by  means  of 
apertures  placed  on  the  sides  of  the  neck. 

The  Hag-fish  (Myxine)  is  an  eel-like  fish,  which  agrees 
with  the  Lampreys  in  having  neither  pectoral  nor  ventral  fins, 
the  representatives  of  the  fore  and  hind  limbs.  The  mouth  is 
of  a  very  remarkable  character,  and  enables  the  Hag-fish  to 
lead  a  very  peculiar  existence.  It  is  generally  found  imbedded 
in  the  interior  of  some  large  fish,  into  which  it  has  penetrated 
by  means  of  a  single  serrated  and  recurved  fang  attached  to 
the  centre  of  the  palate.  The  mouth  itself  is  destitute  of 
jaws,  and  forms  a  sucking  disk  or  cup.  Another  remarkable 
peculiarity  of  the  Hag-fishes  is  found  in  the  structure  of  the 
nose.  In  all  fishes,  namely,  except  these  and  the  Mud-fish 
(Lepidosiren\  the  nasal  chambers  are  closed  behind,  and  do 
not  communicate  with  the  cavity  of  the  mouth,  as  they  do  in 
the  higher  Vertebrates.  In  the  Myxinoids,  however,  such  a 
communication  does  exist.  The  nasal  sacs  are  placed  in  com- 
munication with  the  throat  (pharynx)  by  means  of  a  canal 
which  perforates  the  palate.  A  second  canal  leads  from  the 
nasal  cavities  in  front  to  open  by  an  external  aperture  (the 
nostril  or  "spiracle")  on  the  top  of  the  head  behind  the 
mouth. 

Another  peculiarity,  which  is  best  considered  in  the  Lam- 
preys, is  to  be  found  in  the  structure  of  the  respiratory  or- 
gans, from  which  the  name  of  the  order  is  derived.  ^  When 
viewed  externally,  instead  of  the  single  great  "  gill-slit,"  cov- 
ered by  a  "  gill-cover,"  as  seen  in  the  ordinary  bony-fishes,  the 
side  of  the  neck  presents  seven  round  holes  placed  far  back 
in  a  line  on  each  side.  These  holes  are  the  external  apertures 
of  the  gills  (Fig.  106,  A),  which  in  these  fishes  are  in  the 
form  of  sacs  or  pouches,  the  lining  membrane  of  which  is 
thrown  into  numerous  folds  or  plaits,  over  which  the  branchial 


ORDERS  OF  FISHES.  217 

vessels  ramify  (Fig.  106,  B).  Internally  the  sacs  communi- 
cate with  the  cavity  of  the  pharynx,  by  means  of  a  common 
respiratory  tube  into  which  they  all  open.  It  follows  from 
this  arrangement  that  the  gill-pouches  on  the  two  sides  of  the 
neck  communicate  freely  with  one  another  through  the  phar- 
ynx. The  object  of  this  arrangement  is  to  obviate  the  ne- 
cessity for  admitting  the  water  to  the  gills  through  the  mouth, 


FIG.  106.— A,  Lamprey  (Petromyzon\  showing  the  sucking-mouth  and  the  apertures  of 
the  gill-sacs.  B,  Diagram  to  illustrate  the  structure  of  the  gills  in  the  Lampreys,  a 
Pharynx ;  b  Tube  leading  from  the  pharynx  into  one  of  the  gill-sacs ;  c  One  of  the  gill- 
sacs,  showing  the  lining  membrane  thrown  into  folds ;  d  External  opening  of  the  gill- 
sac.  (In  reality  the  gill-sacs  do  not  open  directly  into  the  pharynx,  but  into  a  common 
respiratory  tube  which  communicates  with  the  pharynx ;  but  this  is  omitted  for  the 
sake  of  clearness.) 

as  ordinary  fishes  do.  These  fishes  are  in  the  habit  of  fixing 
themselves  to  foreign  objects  by  means  of  the  suctorial  mouth ; 
and,  when  in  this  position,  it  is,  of  course,  impossible  that 
they  can  obtain  the  necessary  water  of  respiration  through  the 
mouth.  As  the  gill-sacs,  however,  on  the  two  sides  of  the 
neck  communicate  freely  with  one  another  through  the  phar- 
ynx, water  can  readily  pass  in  and  out.  The  gills  are  not 
provided  with  cilia,  but  the  circulation  of  water  is  assisted  by 
a  kind  of  elastic  cartilaginous  framework  upon  which  the 
whole  respiratory  apparatus  is  supported,  and  which  acts  some- 
what like  the  ribs  of  the  higher  Vertebrates. 

The  nasal  cavities  of  the  Lampreys,  unlike  those  of  the 
Myxinoids,  are  closed  behind,  and  do  not  communicate  with 
the  throat.  Some  of  the  Lampreys  are  permanently  inhabit- 
ants of  rivers,  but  the  great  sea-lamprey  (Petromyzon  mari- 
nus)  only  quits  the  salt  water  and  betakes  itself  to  fresh  in 
order  to  deposit  its  eggs. 

ORDER  III.  TELEOSTEI  (Gr.  teleios,  perfect;  and  osteon, 
bone). — The  fishes  comprised  in  this  order,  as  implied  in  their 
name,  have  a  well-ossified  or  bony  skeleton,  and  they  are  com- 


218  VERTEBRATE  ANIMALS. 

monly  known  as  the  "  bony  "  fishes.  In  all  the  Teleostei,  the 
skeleton  is  bony,  the  skull  is  composed  of  distinct  bones,  and 
there  is  a  lower  jaw.  The  vertebral  column  always  consists 
of  more  or  less  completely  ossified  vertebras;  and  the  two 
pairs  of  limbs,  when  present,  are  in  the  form  of  fins,  supported 
by  rays.  The  gills  are  free,  comb-like  or  tufted  in  shape,  and 
always  protected  by  a  bony  gill-cover.  The  bulbus  arteriosus 
is  not  capable  of  regular  contractions,  and  is  separated  from 
the  ventricle  by  only  a  single  valve. 

The  order  Teleostei  comprises  almost  all  the  most  familiar 
fishes,  and  it  will  be  unnecessary  to  dilate  here  upon  their 
structure,  as  they  were  taken  as  the  type  of  the  class  in  de- 
scribing the  fishes  generally.  It  may  be  as  well,  however,  to 
recapitulate  some  of  the  leading  points  in  the  anatomy  of  the 
bony  fishes.  1.  The  skeleton  is  always  more  or  less  complete- 
ly ossified,  and  does  not  remain  cartilaginous  throughout  life. 
The  notochord  is  not  permanent,  and  the  vertebral  column 
consists  of  a  number  of  distinct  vertebras.  The  vertebras, 
however,  are  "  amphiccelous,"  or  hollow  at  both  ends,  so  that 
there  is  left  between  each  pair  a  doubly-conical  cavity,  which 
is  filled  with  the  cartilaginous  or  semi-gelatinous  remains  of 
the  notochord.  In  this  way  an  extraordinary  amount  of  flexi- 
bility is  given  to  the  entire  vertebral  column.  In  no  fish  (ex- 
cept the  Bony  Pike,  which  belongs  to  another  order)  is  the 
conversion  of  the  bodies  of  the  vertebras  into  bone  carried 
further  than  this. 

2.  The  integument  usually  develops  scales,  and  these  in 
the  great  majority  of  cases  are  of  the  forms  known  as  "  cy- 
cloid "  and  "  ctenoid,"  the  former  being  circular  or  elliptical 
horny  plates,  with  plain  margins  ;  while  the  latter  have  their 
hinder  margins  cut  into  comb-like  projections,  or  fringed  with 
spines  (Fig.  100,  a,  b). 

3.  The  anterior  and  posterior  limbs  are  usually,  but  not 
always,  present,  and  when  developed  they  are  always  in  the 
form  of  tins.     These  fins  may  be  supported  by  "  spinous  rays  " 
or  "  soft  rays,"  or  by  both.    .  The  spinous  rays  are  simple  un- 
divided bony  spines  which  taper  to  a  point.     The  soft  rays 
are  doubly  divided,  splitting  up  toward  their  extremities  into 
a  number  of  secondary  rays,  and  being  also  divided  by  trans- 
verse joints  into  numerous  short  pieces. 

4.  Besides  the  "  paired  "  fins  which  represent  the  limbs, 
there  is  also  a  series  of  unpaired  or  "  median  "  fins,  the  rays 
of  which  are  supported  upon  a  series  of  dagger-shaped  bones, 
deeply  plunged  in  the  flesh  in  the  middle  line  of  the  body, 


OKDERS   OF  FISHES.  219 

and  known  as  the  "  interspinous  "  bones  (Fig.  101).  The  me- 
dian fins  are  variable  in  number,  but  when  fully  developed 
they  consist  of  one  or  two  fins  on  the  back  (the  dorsal  fins), 
one  or  two  on  the  ventral  surface  (the  anal  fins),  and  one 
clothing  the  posterior  extremity  of  the  body  (the  caudal  fin, 
or  tail,  Fig.  102).  In  all  the  Teleostei,  the  caudal  fin  has  the 
shape  called  "  homocercal " — that  is  to  say,  it  consists  of  two 
equal  lobes — and  the  vertebral  column  is  not  prolonged  into 
the  upper  lobe  (Fig.  103,  a}. 

5.  The  heart  consists  of  two  cavities,  an  auricle  and  a  ven- 
tricle, but  the  bulbus  arteriosus  is  not  rhythmically  contractile, 
and  is  separated  from  the  ventricle  by  only  a  single  pair  of 
valves. 

6.  The  respiratory  organs  are  in  the  form  of  free,  comb- 
like,  or  tufted  gills,  enclosed  in  two  cavities  placed  on  the 
sides  of  the  neck.     Each  of  these  branchial  chambers  opens 
externally  by  a  single  aperture,  the  "  gill-slit,"  which  is  pro- 
tected by  a  chain  of  bones,  forming  the  "  gill-cover,"  and  by 
a  membrane  supported  by  bony  rays.    Internally  the  branchial 
chambers  communicate  with  the  throat  by  a  series  of  clefts  or 
fissures,  and  the  water  required  in  respiration  is  taken  in  at 
the  mouth  by  a  process  analogous  to  swallowing. 

7.  The  nasal   sacs   never  communicate  behind  with   the 
throat  (pharynx). 


TABULAR  VIEW  OF  THE  MAIN  DIVISIONS  OF  THE  TELEOSTEI. 

SUB-ORDER  I.  MALACOPTERI. — Usually  a  complete  series  of  fins,  supported 
by  rays,  all  of  which  are  soft,  or  many-jointed  (with  the  occasional  exception 
of  the  first  rays  in  the  dorsal  and  pectoral  fins).  A  swim-bladder  is  always 
present,  and  is  always  connected  with  the  gullet  by  a  duct.  The  skin  is  rarely 
naked,  and  is  mostly  furnished  with  cycloid  scales,  but  sometimes  ganoid 
scales  are  present. 

Among  the  more  important  families  in  this  sub-order  are  the  Eels  (Mu- 
rcenidce),  Herrings  (Clupeidce],  Pikes  (Esoddce),  Carps  (Cyprinidce),  Salmon 
and  Trout  (Salmonidai),  and  Sheat-fishes  (Siluridce). 

SUB-ORDER  II.  ANACANTHINI. — Fins  entirely  supported  by  soft  rays,  and 
never  by  spinous  rays.  Ventral  fins  either  wanting,  or  placed  under  the 
throat,  beneath  or  in  advance  of  the  pectorals. 

The  two  leading  families  in  this  sub-order  are  the  Cod,  Ling,  and  Haddock 
family  (Gadidce),  and  the  Flat-fishes  (Pleuronectidce\  comprising  the  Sole, 
Turbot,  Flounder,  and  others. 

SUB-ORDER  III.  ACANTHOPTERI. — Fins  with-  one  or  more  of  the  first  rays  in 
the  form  of  undivided,  inflexible,  spinous  rays.  Scales  mostly  ctenoid.  Swim- 
bladder  without  a  duct. 

The  leading  families  in  this  order  are  the  Wrasses  ( Cyclo-labridce\  the 
Perches  (Percidce),  the  Mackerels  (Scomberidce),  the  Mullets  (Mugilidce],  and 
the  Gobies  (Gobiidce). 


220  VERTEBRATE  ANIMALS. 

SUB-ORDER  IV.  PLECTOGNATHI. — Certain  of  the  bones  of  the  mouth  (the 
maxillary  and  prae-maxillary  bones)  immovably  connected  on  each  side  of 
the  jaw.  Integumentary  skeleton  in  the  form  of  ganoid  plates,  scales,  or 


The  chief  families  in  this  sub-order  are  the  File-fishes  (Balislidce),  and  the 
Trunk-fishes  ( Ostraciontidce). 

SUB-ORDER  V.  LOPHOBRANCHII. — Gills  arranged  in  little  tufts  on  the 
branchial  arches.  Integumentary  skeleton  in  the  form  of  ganoid  scales. 

The  two  families  contained  in  this  division  are  the  Sea-horses  (Hippocam- 
pidce),  and  the  Pipe-fishes  (Syngnathidce). 

OEDEK  IV.  GANOIDEI  (Gr.  ganos,  splendor,  or  brightness). 
— The  fourth  order  of  fishes  is  that  of  the  G-anoidei,  including 
few  living  forms,  but  having  a  great  and  varied  development 
in  past  geological  epochs.  The  Ganoid  fishes  are  dis- 
tinguished by  the  imperfect  development  of  the  skeleton, 
which  is  mostly  cartilaginous  throughout  life.,  and  by  having 
an  integumentary  skeleton  composed  of  ganoid  scales,  plates, 
or  spines  (Fig.  100,  d).  The  skull  is  composed  of  distinct 
bones,  and  there  is  always  a  lower  jaw.  There  are  usually 
two  pairs  of  fins  (pectoral  and  ventral),  supported  by  many 
series  of  cartilages,  and  the  ventral  fins  are  placed  very  far 
back.  The  first  rays  in  the  fins  are  usually  in  the  form  of 
strong  spines.  The  caudal  fin  or  tail  is  mostly  heterocercal 
or  unsymmetrical  (Fig.  103,  #).  The  swim-bladder  is  always 
present,  is  often  cellular,  and  is  provided  with  an  air-duct. 
The  gills  and  gill-covers  are  essentially  the  same  as  in  the 
bony  fishes.  The  heart  has  one  auricle  and  a  ventricle  ;  and 
the  bulbus  arteriosus  is  rhythmically  contractile,  is  furnished 
with  a  distinct  coat  of  muscular  fibres,  and  is  furnished  with 
several  transverse  rows  of  valves. 

The  best  known  of  the  living  Ganoids  are  the  Bony  Pike 
(Lepidosteus),  the  Sturgeon  (Sturio),  and  the  Polypterus.  Of 
these,  the  Bony  Pike  is  found  in  the  rivers  and  lakes  of  North 
America.  It  is  a  large  fish,  attaining  a  length  of  several  feet, 
and  it  has  the  body  entirely  covered  with  an  armor  of  ganoid 
scales  arranged  in  obliquely  transverse  rows.  The  jaws  form 
a  long,  narrow  snout,  armed  with  a  double  series  of  teeth,  and 
the  tail  is  heterocercal.  The  vertebral  column  is  more  perfect- 
ly ossified  than  in  any  other  fish,  the  bodies  of  the  vertebras 
being  convex  in  front  and  concave  behind  (  "  opisthocoelous  "). 
The  Polypterus  (Fig.  107,  A)  inhabits  the  rivers  Nile  and 
Senegal,  and  is  remarkable  for  the  peculiar  structure  of  the 
dorsal  fin,  which  is  broken  up  into  a  series  of  small,  detached 
portions,  each  composed  of  a  single  spine  in  front,  with  a  soft 
fin  attached  to  it  behind.  Some  of  the  species  of  Polypterus 


ORDERS   OF  FISHES. 

d 


221 


FIG.  107. — Ganoid  Fishes.    A,  Poli/pterus,  a  living1  Ganoid.    B,  Osteolepis,  a  fossil  Ganoid 
(restored) :  a  Pectoral  fin ;  b  Ventral  fin ;  c  Anal  fin ;  d  d'  Dorsal  fins. 

are  stated  to  possess  external  gills  when  young,  which  they 
lose  when  grown  up,  thus  making  an  approach  to  the  Am- 
phibia. Many  of  the  fossil  Ganoids  are  more  or  less  closely 
allied  to  the  living  Lepidosteus  and  Polypterus. 

Another  great  group  of  the  Ganoid  fishes  is  represented  by 
the  Sturgeons  (Sturiom<tce\  in  which  the  skeleton  is  always 
very  imperfectly  ossified,  and  the  head,  with  more  or  less  of 
the  body,  is  protected  by  large  ganoid  plates,  which  are  often 
united  together  at  their  edges  by  sutures.  The  true  Sturgeons 
are  chiefly  found  in  the  North  Sea,  the  Caspian,  and  the  Black 
Sea,  and  they  are  captured  when  ascending  the  great  rivers 
for  the  purpose  of  spawning.  The  swim-bladder  of  the  Stur- 
geons is  one  of  the  chief  sources  from  which  isinglass  is  pre- 
pared, and  the  roe  is  sold  as  a  delicacy  under  the  name  of 
caviare.  The  place  of  the  Sturgeons  in  North  America  is 
taken  by  the  Paddle-fishes  (Spatularia). 

The  group  of  Ganoids  represented  at  the  present  day  by 
the  Sturgeons  and  Paddle-fishes  was  formerly  represented  by 
numerous  remarkable  fishes,  which  are  most  abundant  in  the 
system  of  rocks  known  to  geologists  as  the  "  Old  Red  Sand- 
stone." The  graphic  descriptions  of  Hugh  Miller  have  placed 
many  of  these  fishes  before  us  as  living  pictures,  but  space 
will  not  allow  of  any  further  notice  of  them  here.  One,  how- 
ever, of  the  more  striking  forms  is  figured  hereafter  (Fig.  108). 

ORDER  V.  ELASMOBRANCHII  (Gr.  elasma,  a  thin  plate ;  and 
bragchia,  gills). — This  order  includes  the  Sharks  and  Rays, 


222 


VERTEBRATE  ANIMALS. 


and  is  distinguished  by  the  following  characters :  The  skull 
and  lower  jaw  are  well  developed,  but  the  skull  is  not  com- 


Fio.  108.— Cephalaspia  LyelUi,  from  the  Old  Bed  Sandstone  of  Scotland. 

posed  of  distinct  bones,  and  simply  forms  a  kind  of  cartila- 
ginous box.  The  vertebral  column  is  sometimes  cartilaginous, 
sometimes  composed  of  distinct  vertebrae.  The  integument- 
ary skeleton  is  in  the  form  of  placoid  scales  (Fig.  100,  c) — 


FIG.  109.— Elasmobranchii. 


A.  White  Shark  (Carcharias). 
(Chimwrd). 


B.  King  of  the  Herrings 


ORDERS  OF  FISHES.  223 

that  is  to  say,  of  detached  grains,  tubercles,  or  plates.  There 
are  two  pairs  of  fins,  corresponding  to  the  fore  and  hind  limbs, 
and  the  ventral  fins  are  placed  far  back,  close  to  the  anus. 
The  heart  consists  of  an  auricle  and  ventricle ;  and  the  bulbus 
arteriosus  is  rhythmically  contractile,  is  provided  with  a  dis- 
tinct coat  of  muscular  fibres,  and  is  furnished  with  several 
transverse  rows  of  valves.  The  gills  are  fixed,  and  form  a 
number  of  pouches,  which  open  internally  into  the  pharynx, 
and  communicate  with  the  outer  world  by  a  series  of  aper- 
tures placed  on  the  side  of  the  neck  (Fig.  109).  The  intestine 
is  very  short,  but,  to  compensate  for  this,  the  mucous  mem- 
brane is  thrown  into  a  fold,  which  winds  round  the  intestine 
in  close  turns  from  the  pyloric  orifice  of  the  stomach  to  the 
anus,  and  which  thus  greatly  increases  its  absorbing  surface. 

The  best-known  members  of  this  order  are  the  Sharks  and 
Rays,  but  numerous  extinct  forms  testify  to  its  great  abun- 
dance in  past  geological  epochs. 


TABULAR  VIEW  OP  THE  DIVISIONS  OF  THE  ELASMOBRANCHII. 

SUB-ORDER  I.  HOLOCEPHALI. — The  mouth  placed  at  the  end  of  the  head, 
and  the  external  opening  of  the  gills  in  the  form  of  a  single  gill-slit. 

The  best-known  member  of  this  sub-order  is  the  Chimcera  monstrosa, 
sometimes  called  the  "King  of  the  Herrings." 

SUB-ORDER  II.  PLAGIOSTOMI. — Mouth  transverse,  placed  on  the  under  sur- 
face of  the  head  ;  external  opening  of  the  gills  in  the  form  of  several  slits  on 
each  side  of  the  neck,  not  protected  by  a  gill-cover. 

Fam.  a.  Cestrapkori. — Ex.  Port-Jackson  Shark. 

Fam.  b.  Selachii. — Ex,.  Sharks  and  Dog-fishes. 

Fam.  c.  Batides. — Ex.  Rays. 

ORDER  VI.  DIPNOI  (Gr.  di,  double ;  pnoe,  breath). — This 
order  is  a  very  small  one,  and  includes  only  the  very  singular 
Mud-fishes  (Lepidosireri)*  which  are  of  great  interest  from 
the  many  points  of  affinity  which  they  exhibit  to  the  Am- 
phibia. The  body  of  the  Mud-fish  (Fig.  110)  is  completely 
fish-like,  and  is  protected  by  a  covering  of  small,  horny,  over- 
lapping scales,  which  have  the  cycloid  characters.  There  are 
two  pairs  of  limbs,  but  these  are  in  the  form  of  awl-shaped 
organs,  each  supported  by  a  single  jointed  cartilaginous  rod. 
The  pectoral  limbs  have  a  membranous  fringe  inferiorly,  and 
the  ventrals  are  placed  very  far  back.  There  is  also  a  median 

*  Recently  a  singular  fish  has  been  discovered  in  the  rivers  of  Queensland  (Australia), 
which  will  probably  have  to  be  referred  to  the  order  Dipnoi  ;  but  our  knowledge  about  it  is 
etill  imperfect. 


224  VERTEBRATE  ANIMALS. 

fin  behind,  forming  a  continuous  fringe  round  the  compressed 
tail,  and  supported  by  cartilaginous  rays. 


P 
FIG.  110.— Lepid o#iren  annectens,  the  Mud-fish,   p  Pectoral  limbs ;  v  Ventral  limbs. 

The  skull  is  composed  of  distinct  bones,  and  there  is  a 
lower  jaw,  but  the  notochord  is  persistent,  and  there  are  no 
bodies  of  vertebrae  developed.  The  respiratory  organs  are 
twofold,  consisting,  firstly,  of  free  filamentous  branchiae  or 
gills,  contained  in  a  branchial  chamber,  which  opens  externally 
by  a  single  vertical  gill-slit ;  and,  secondly,  of  true  lungs,  in 
the  form  of  a  double  cellular  air-bladder  communicating  with 
the  gullet  by  means  of  an  air-duct  or  windpipe.  Sometimes, 
if  not  always,  there  are  rudimentary  external  gills  as  well, 
placed  on  the  side  of  the  neck.  The  heart  consists  of  a  ven- 
tricle, and  of  two  auricles,  divided  from  one  another  by  an 
incomplete  partition.  Lastly,  the  nasal  sacs  open  behind  into 
the  throat,  and  do  not  form  closed  chambers  opening  only  by 
the  nostrils,  as  they  do  in  all  other  fishes,  except  the  Myxi- 
noids.  The  two  best-known  species  are  the  Lepidosiren 
paradoxa  from  the  Amazons,  and  the  L.  annectens  from  the 
Gambia.  They  both  inhabit  marshy  tracts,  and  both  appear 
to  be  able  in  the  dry  season  to  bury  themselves  in  the  mud, 
and  to  form  a  kind  of  chamber,  in  which  they  remain  dormant 
till  the  rains  of  the  wet  season  set  them  free 


I  C  H  T  H  TOPS  ID  A. 
CHAPTER  XXVI. 

CLASS     II.     AMPHIBIA. 

THIS  class  of  Yertebrata  comprises  the  Frogs  and  Toads, 
the  Newts  and  Land-salamanders,  the  Ccecilice,  and  some  ex- 
tinct forms,  and  it  may  be  briefly  defined  as  follows :  In  all 
cases  gills  or  branchiae  adapted  for  aquatic  respiration  are  pres- 
ent during  a  part  or  the  whole  of  life ;  but,  in  all  cases,  true 
lungs  adapted  for  breathing  air  are  ultimately  developed,  even 
when  the  gills  are  retained  through  life.  All  pass  through 
some  sort  of  a  metamorphosis  after  being  set  free  from  the 
egg.  The  limbs  may  be  absent  or  there  may  be  only  one 
pair,  but  in  no  case  are  they  ever  converted  into  fins.  When 
median  fins  are  present,  as  is  sometimes  the  case,  these  are 
never  furnished  with  fin-rays  or  interspinous  bones,  as  in  the 
fishes.  The  skull  always  articulates  with,  or  is  jointed  to,  the 
spinal  column  by  two  articular  surfaces  or  condoles.  The 
heart  consists  of  two  auricles  and  a  single  ventricle.  The  na- 
sal sacs  always  open  behind  into  the  mouth ;  and  there  is  a 
common  cavity  or  "  cloaca  "  which  receives  not  only  the  ter- 
mination of  the  intestine  (rectum),  but  also  the  ducts  of  the 
kidneys  and  of  the  reproductive  organs. 

The  great  and  distinguishing  character  of  the  Amphibia 
(Gr.  amphi,  both  ;  bios,  life)  is,  that  they  invariably  undergo 
some  kind  of  metamorphosis  after  birth,  though,  in  some  rare 
cases,  the  eggs  are  retained  so  long  within  the  body  of  the 
parent  that  there  is  little  or  no  obvious  change.  In  the  great 
majority  of  cases,  however,  the  Amphibians  commence  life  as 
water-breathing  larva?,  provided  with  gills  ;  but,  in  their  adult 
state,  they  possess  true  air-breathing  lungs,  the  gills  sometimes 
disappearing  when  the  lungs  are  developed,  but  being  some- 


226  VERTEBRATE  ANIMALS. 

times  retained  throughout  life.  Most  Amphibians,  therefore, 
are  to  a  greater  or  less  extent  amphibious,  that  is  to  say, 
more  or  less  capable  of  living  indifferently  .either  on  land  or 
in  the  water.  In  the  majority  of  cases,  the  gills  arc  external, 
placed  on  the  sides  of  the  neck,  and  not  contained  in  a  special 
cavity,  thus  differing  altogether  from  the  gills  of  fishes.  In 
the  Frogs  and  Toads,  and  in  some  others,  there  are  two  sets 
of  gills,  one  external  and  the  other  internal,  of  which  the  for- 
mer is  soonest  lost.  The  lungs  of  the  Amphibians  never  attain 
a  very  high  state  of  development,  and,  in  those  forms  in  which 
the  gills  are  retained  throughout  life,  the  chief  business  of 
respiration  appears  to  be  carried  on  by  the  gills.  In  accord- 
ance with  the  changes  in  the  respiratory  process,  correspond- 
ing alterations  take  place  in  the  blood-vessels.  With  the 
development  of  the  lungs,  the  vessels  which  carry  blood  to 
them  (the  pulmonary  arteries)  increase  in  size,  while  the 
branchial  vessels  which  carry  the  blood  to  the  gills  undergo  a 
proportionate  diminution.  At  first,  the  condition  of  the  circu- 
lation is  very  much  the  same  as  it  is  in  fishes,  but  ultimately 
it  becomes  nearly  the  same  as  in  the  true  reptiles. 

The  Amphibia  are  divided  into  three  living  and  one  ex- 
tinct order,  as  follow : 

1.  Ophiomorpha. 

2.  Urodela. 

3.  A.noura. 

4.  Ldbyrintliodontia. 


ORDER  I.  OPHIOMORPHA  (Gr.  ophis,  a  serpent ;  and  morphe, 
form). — This  order  is  an  extremely  small  one,  and,  as  its  name 
implies,  it  comprises  certain  snake-like  Amphibians.  The  order 
includes  only  the  curious  animals  known  as  Ccecilice,  which  are 
found  in  Java,  Ceylon,  South  America,  and  Guinea.  The  body  is 
entirely  destitute  of  limbs,  and  is  enclosed  in  an  integument 
which  is  thrown  into  numerous  transverse  wrinkles,  and  some- 
times has  numerous  horny  scales  imbedded  in  it.  The  eyes  are 
concealed  by  the  skin,  and  are  rudimentary.  There  is  no  tail, 
and  the  anal  aperture  is  placed  almost  at  the  extreme  end  of 
the  body.  When  adult,  respiration  is  carried  on  by  means  of 
lungs,  but  gills  are  present  in  the  young,  and  there  can,  there- 
fore, be  no  doubt  as  to  their  being  genuine  Amphibians. 

The  CcecilicB  are  found  burrowing  in  marshy  ground,  and 
they  are  not  unlike  large  earth-worms  in  appearance,  but  they 
sometimes  attain  a  length  of  several  feet. 


AMPHIBIA. 


227 


FIG.  HI- — o>  SipJionops  annulatus,  one  of  tho  Caecilians,  much  reduced  ;  &  Head  of  the 
same ;  c  Mouth,  showing  the  tongue,  teeth,  and  internal  openings  of  the  nostrils ;  d 
Tail  of  the  same.  (After  Dumeril  and  Bibron.) 


ORDER  II.  URODELA  or  ICHTHYOMORPHA  (Gr.  ichthus,  a 
fish,  and  morphe,  shape). — In  this  order  are  a  number  of  fish- 
like  Amphibians,  of  which  the  Newts  and  Land-salamanders 
are  the  most  familiar  examples.  In  all  the  members  of  this 
section,  the  skin  is  naked,  and  never  develops  any  hard  struct- 
ures, and  in  all  there  is  a  well-developed,  fish-like  tail,  which 
is  retained  throughout  life.  The  vertebras  are  sometimes  hol- 
low at  both  ends  (amphiccelous),  sometimes  hollow  behind 
and  convex  or  rounded  in  front  (opisthocoelous).  The  ribs  are 
rudimentary  and  the  bones  of  the  forearm  (radius  and  ulna\ 
and  of  the  shank  (tibia  and^frw/a),  are  separate,  and  are  not 
combined  so  as  to  form  single  bones. 

The  Ichthyomorpha  are  not  unfrequently  spoken  of  as  the 
"Tailed"  Amphibians  (Urodeld),  and  they  fall  into  two  natu- 
ral sections,  according  as  the  gills  are  permanently  retained 
throughout  life,  or  are  cast  off  before  maturity  is  attained. 
The  animals  belonging  to  the  first  section  are  often  called 
"  perennibranchiate,"  while  those  belonging  to  the  second  are 
said  to  be  "  caducibranchiate." 

Among  the  Perennibranchiate  forms,  in  which  the  gills  are 
permanently  retained  after  the  lungs  make  their  appearance, 
the  best-known  examples  are  Axolotl  (Fig.  112),  the  curious 
Proteus  anguinus,  and  the  Mud-eel  (Siren).  The  Axolotls 


228  VERTEBRATE  ANIMALS. 

inhabit  various  of  the  lakes  of  the  American  Continent,  the  best- 
known  species  being  the  Siredon  pisciforme  of  the  Mexican 
lakes  (Fig.  112).  It  attains  a  length  of  a  foot  or  more,  and 


FIG.  112.— The  Axolotl  (Siredon  pisciforme).    (After  Tegetmeier.) 

possesses  both  pairs  of  limbs,  the  fore-feet  having  four  toes, 
the  hind-feet  five  toes.  The  branchiae  are  in  the  form  of  three 
long  ramified  processes  on  each  side  of  the  head ;  and  the  tail 
is  compressed,  and  fringed  by  a  fin  which  is  prolonged  on  the 
back  between  the  shoulders.  In  a  state  of  nature,  the  Axolotl 
is  certainly  perennibranchiate,  and  it  breeds  freely  in  this 
condition.  It  has  been  shown,  however,  by  Prof.  Marsh,  of 
New  Haven,  that  some  species,  when  kept  in  confinement,  lose 
their  gills,  and  undergo  certain  other  changes,  becoming  ul- 
timately converted  into  a  Salamandroid,  apparently  belonging 
to  the  genus  Amblystoma.  The  Proteus  is  an  extraordinary 
Amphibian  which  is  found  inhabiting  the  waters  of  caves  in 
Illyria  and  Dalmatia.  It  attains  a  length  of  about  a  foot,  and 
is  of  a  pale  flesh-color  or  nearly  white.  The  gills,  which  are 
retained  throughout  life,  are  of  a  bright  scarlet.  Both  pairs 
of  limbs  are  developed,  but  they  are  only  short  and  weak,  the 
fore-limbs  having  three  toes  each,  and  the  hind-limbs  only 
two.  The  eyes  are  extremely  small,  the  animal  spending  its 
existence  in  darkness;  and  swimming  is  effected  mainly  by 
means  of  the  tail.  The  Siren,  or  Mud-eel,  is  a  large  lizard-like 
Amphibian,  which  is  found  abundantly  in  the  swamps  of  South 
Carolina,  and  attains  the  great  length  of  three  feet.  The  ex- 
ternal branchiae  are  retained  throughout  life,  and  they  are  the 
main  organs  of  respiration.  The  fore-limbs  are  present,  but 
the  hinder  pair  of  limbs  is  never  developed. 


AMPHIBIA.  229 

The  "  caducibranchiate "  section  of  this  order  is  charac- 
terized by  the  fact  that  both  pairs  of  limbs  are  always  de- 
veloped, and  the  branchiae  are  never  retained  throughout  life. 
The  most  familiar  examples  are  the  Water-salamanders  or 
Newts  (Triton),  and  the  Land-salamanders.  The  Newts  (Fig. 
113)  are  well  known  as  inhabiting  pools  in  many  countries, 


FIG.  113.— The  great  Water-Newt  (Triton  cristatm),  male.    (After  Bell.) 

and  the  young  lead  a  strictly  aquatic  life.  When  the  lungs 
are  developed  the  external  gills  wholly  disappear,  and  the 
respiration  becomes  strictly  aerial,  though  the  animals  still 
spend  a  great  part  of  their  time  in  the  water.  The  larva  or 
young  form  is  at  first  destitute  of  limbs,  and  the  fore-limbs  are 
the  first  to  be  developed,  the  reverse  of  this  taking  place  in 
the  Frogs.  In  accordance  with  their  mode  of  life,  the  tail  is 
compressed  and  flattened,  so  as  to  form  an  efficient  swimming 
apparatus.  The  Water-salamanders  are  all  oviparous,  and  the 
young  are  like  the  tadpoles  of  the  common  frog. 

The  Land-salamanders,  in  both  their  adult  and  young 
state,  live  upon  land,  and  the  tail  is  rounded  and  cylindrical. 
The  yeung  are  not  developed  in  water,  but  are  retained  with- 
in the  body  of  the  parent  for  a  longer  or  shorter  period,  so 
that  the  reproduction  becomes  ovo-viviparous,  or  even  vivip- 
arous. The  best-known  Salamanders  occur  upon  the  Con- 
tinent of  Europe,  and  one  species  is  singular  in  the  fact  that 
it  inhabits  high  mountains. 

It  is  important  to  remember  in  connection  with  all  these 
"  tailed  "  Amphibians,  that  they  are  wholly  distinct  from  the 
true  Lizards,  with  which  they  are  often  confounded.  Many 
of  them  are  completely  lizard-like  in  form,  having  a  long  tail 
and  two  pairs  of  legs ;  all,  however,  at  some  time  or  other  in 
their  life,  respire  by  means  of  gills,  and  this  is  never  the  case 
with  any  true  Lizard.  It  must  be  confessed,  however,  that  a 


230  VERTEBRATE  ANIMALS. 

near  approach  to  the  Lizards  is  made  by  the  Land-salamanders, 
the  young  of  which  have  sometimes  lost  their  gills  before 
birth. 

ORDER  III.  ANOURA  or  THERIOMORPHA  (Gr.  ther,  a  beast ; 
and  morphe,  shape). — This  order  is  the  highest  of  the  Am- 
phibia, and  comprises  the  Frogs  and  Toads.  It  is  sometimes 
known  by  the  name  of  JBatrachia  (Gr.  batrachos,  a  frog),  or 
Anoura  (Gr.  a,  without;  our  a,  a  tail),  the  latter  name  being 
derived  from  the  fact  that  the  adults  are  "  tailless." 

The  tailless  Amphibia  or  Theriomorpha  are  characterized 
by  the  fact  that  while  the  larva  possesses  a  tail,  and  is  fur- 
nished with  gills,  the  adult  has  no  tail,  and  breathes  wholly 
by  lungs.  Both  pairs  of  limbs  are  always  developed  in  the 
full-grown  animal,  and  the  hind-limbs  are  usually  considerably 
longer  than  the  fore-limbs,  and  generally  have  the  toes 
webbed,  while  those  of  the  fore-limbs  are  free.  The  skin  is 


FIG.  114.— Anoura.    Tree-frog  (Hyla  leucotcenia),    (After  Gunther.) 

soft,  and  there  are  rarely  any  traces  of  any  integumentary 
skeleton.  The  spinal  column  (Fig.  114)  is  short ;  the  dorsal 
vertebrae  are  very  long ;  and  the  ribs  are  quite  rudimentary, 
their  place  being  taken  by  greatly-developed  transverse  pro- 
cesses. The  bodies  of  the  vertebrae  are  hollow  in  front  and 
convex  behind  (proccelous).  The  bones  of  the  forearm  (radius 
and  ulna),  and  those  of  the  shank  (tibia  &ud  fibula),  are  united 
together  to  form  single  bones.  The  upper  jaw  is  usually  fur- 


AMPHIBIA. 


231 


nished  with  teeth,  and  the  lower  jaw  sometimes,  but  there 
are  no  teeth  in  the  Toads.  The  lungs  are  well  developed, 
comparatively  speaking ;  and,  as  there  are  no  ribs  by  which 
the  cavity  of  the  chest  can  be  expanded,  the  air  is  taken  into 
the  lungs  by  a  process  nearly  akin  to  that  of  swallowing. 
There  can  be  no  doubt,  also,  that  the  skin  plays  a  very  im- 
portant part  in  the  aeration  of  the  blood,  and  that  the  frogs, 
especially,  can  carry  on  their  respiration  by  means  of  the  skin 
without  the  assistance  of  the  lungs  for  a  very  lengthened 
period.  This,  however,  should  not  lead  to  any  credence  being 
given  to  the  often-repeated  stories  of  frogs  and  toads  being 
found  in  closed  cavities  in  solid  rock,  no  authenticated  instance 
of  such  an  occurrence  being  known  to  science.  The  ova  of 
the  frogs  and  toads  are  deposited,  in  masses  or  strings,  in 
water,  and  the  young  or  larvae  are  familiar  to  every  one  as 
tadpoles.  Upon  its  escape  from  the  egg,  the  young  frog  (Fig. 


FIG.  115.— Development  of  the  common  Frog,  a  Tadpole,  viewed  from  above,  showing  the 
external  branchiae  (Q)  ;  6  Side  view  of  a  somewhat  older  specimen,  showing  the  fish-like 
tail ;  c  Older  specimen,  in  which  the  hind-legs  have  made  their  appearance ;  d  Specimen 
in  which  all  the  limbs  are  present,  but  the  tail  has  not  been  wholly  absorbed.  (After 
Beii.) 

115)  presents  itself  as  a  little  fish-like  creature  with  a  broad 
head,  a  sac-like  belly,  and  a  long,  compressed  tail  with  which 
it  swims  actively.  It  breathes  by  means  of  gills  or  branchiae, 
of  which  there  are  two  sets,  one  external,  and  the  other  in- 
ternal ;  at  first  there  are  no  limbs ;  but,  as  development  pro- 
ceeds, the  limbs  make  their  appearance — the  hind-legs  first, 
and  then  the  fore-legs.  The  tail,  however  (Fig.  115),  is  still 
retained  as  an  instrument  of  progression.  Ultimately,  when 


232  VERTEBRATE  ANIMALS. 

the  limbs  are  fully  developed,  and  the  gills  have  given  place 
to  lungs,  the  tail  disappears,  and  the  animal  now  takes  to  the 
land  as  a  perfect  frog. 

The  development  of  the  Frog  is  a  good  illustration  of  the 
general  zoological  law,  that  the  transitory  embryonic  stages 
of  the  higher  members  of  any  division  of  the  animal  kingdom 
are  often  represented  by  the  permanent  condition  of  the  lower 
members  of  the  same  division.  Thus  the  transitory  condition 
of  the  young  Frog,  in  which  it  breathes  by  external  branchiae, 
is  to  a  certain  extent  permanently  represented  by  the  perma- 
nent condition  of  a  perennibranchiate  Amphibian,  such  as  the 
Proteus.  The  stage  at  which  the  external  branchiae  have  dis- 
appeared, but  the  tail  is  still  present,  and  the  limbs  are  de- 
veloped, is  permanently  represented  in  the  common  tailed 
Amphibians,  such  as  the  Newts. 

The  order  Anoura  comprises  the  three  families  of  the 
Frogs,  Toads,  and  Surinam  Toads.  The  Frogs  (Ranidaz)  are 
distinguished  by  having  a  tongue  which  is  fixed  to  the  front 
of  the  mouth,  and  can  be  protruded  at  will,  while  the  upper 
jaw  is  always  armed  with  teeth.  The  typical  Frogs  have 
enormously-developed  hind  legs,  the  toes  of  which  are  united 
by  membrane,  or  are  "  webbed."  They  swim  very  power- 
fully, and  can  take  extensive  leaps.  The  Tree-frogs  (Fig. 
114),  on  the  other  hand,  are  adapted  for  a  wholly  different 
life,  inhabiting  trees,  among  which  they  climb  with  great  ease 
by  the  help  of  suckers  developed  upon  the  ends  of  the  toes. 
They  are  mostly  found  in  warm  countries,  especially  in  Amer- 
ica, but  one  species  is  European. 

In  the  equally  familiar  Toads  (Bufonidce)  the  structure  of 
the  tongue  is  the  same  as  in  the  Frogs,  but  the  jaws  are  not 
furnished  with  teeth.  In  the  Surinam  Toads  (Pipidce)  there 
is  no  tongue  at  all,  and  usually  no  teeth. 

ORDER  IV.  LABYRrNTHODONTiA. — This,  the  last  order  of 
the  Amphibia,  is  not  represented  by  any  living  forms,  and  re- 
quires to  be  little  more  than  mentioned.  The  Labyrinthodonts 
were  Amphibia  which  were  mostly  of  large  size,  and  of  which 
some  must  have  obtained  absolutely  gigantic  dimensions,  the 
skull  of  one  species  being  three  feet  in  length  and  two  in 
breadth.  They  were  first  known  to  science  simply  by  their 
footprints,  which  were  found  in  certain  Secondary  sandstones 
(Trias).  These  footprints  consisted  of  a  series  of  alternately 
placed  pairs  of  hand-shaped  impressions,  the  hinder  print  of 
each  pair  being  much  larger  than  the  fore  one.  So  like  were 


AMPHIBIA.  233 

these  prints  to  the  shape  of  the  human  hand  that  the  unknown 
animal  which  had  produced  them  was  christened  the  "  Cheiro 
therium  "  (Gr.  cheir,  hand ;  ther,  beast).  Further  researches, 
however,  showed  that  these  footprints  were  produced  by 
various  species  of  large  Amphibians,  to  which  the  name  of 
Ldbyrinthodontia  was  applied,  in  consequence  of  the  compli- 
cated microscopic  structure  of  the  teeth.  These  extinct  Am- 
phibians are  known  to  have  existed  at  the  time  of  the  Coal, 
but  they  are  most  characteristic  of  the  period  known  to  geolo- 
gists as  the  Trias. 


SAUROPSIDA. 

CHAPTER    XXVII. 
CLASS  III.    REPTILIA. 

WE  commence  now  the  second  great  primary  division  of 
the  Vertebrata,  namely,  that  of  the  /Sauropsida,  comprising 
the  Reptiles  and  the  Birds.  These  two  classes,  though  very 
unlike  in  external  appearance,  are  united  by  the  following 
characters :  There  are  never  at  any  period  of  life  gills  or  bran- 
chiae adapted  for  aquatic  respiration ;  the  red  corpuscles  of 
the  blood  are  nucleated  (Fig.  99,  b,  c) ;  the  skull  articulates 
with  the  vertebral  column  by  means  of  a  single  articulating 
surface  or  condyle ;  each  half  of  the  lower  jaw  is  composed 
of  several  pieces,  and  is  jointed  to  the  skull,  not  directly,  but 
by  the  intervention  of  a  special  bone  (the  so-called  "  quadrate 
bone  " ). 

These  being  the  characters  by  which,  among  others,  Rep- 
tiles and  Birds  are  collectively  distinguished  from  other  Ver- 
tebrates, it  remains  to  see  what  are  the  characters  by  which 
the  Reptiles  are  distinguished,  as  a  class,  from  Birds.  In  all 
Reptiles  the  blood  is  cold — that  is  to  say,  very  slightly  warm- 
er than  the  temperature  of  the  external  medium  in  which  they 
live.  The  integument  secretes  scales,  with  or  without  bony 
plates,  but  in  no  case  do  the  integumentary  appendages  take 
the  form  of  feathers.  The  heart  consists  of  two  auricles,  and 
a  ventricle,  which  in  most  is  partially  divided  into  two  cham- 
bers by  an  incomplete  partition,  and  in  a  few  is  completely 
divided.  In  any  case,  however,  more  or  less  of  the  impure 
venous  blood  is  mixed  with  the  pure  arterial  blood  which  cir- 
culates over  the  body.  There  is  no  division  between  the  cavi- 
ties of  the  thorax  and  abdomen,  and  the  lungs  are  not  con- 
nected with  air-sacs  placed  in  various  parts  of  the  body.  The 
limbs  may  be  wanting,  or  rudimentary,  but  in  no  case  are  the 


REPTILIA.  235 

fore-limbs  constructed  upon  the  type  of  the  "  wing  "  of  birds, 
and  in  no  living  Reptile  is  there  the  bone  which  is  known  in 
Birds  as  the  "  tarso-meta tarsus." 

The  class  Reptilia  includes  the  Tortoises  and  Turtles  (  Che- 
Ionia),  the  Snakes  ( Ophidia],  the  Lizards  (Lacertilia),  and  the 
Crocodiles  (Crocodilia).  With  the  exception  of  the  Tortoises 
and  Turtles,  they  are  mostly  of  an  elongated  cylindrical  form, 
furnished  behind  with  a  long  tail.  The  limbs  may  be  alto- 
gether absent  or  quite  rudimentary,  as  in  the  Snakes,  but  in 
almost  all  the  higher  members  of  the  class  there  are  two  pairs 
of  limbs,  which  may  be  either  adapted  for  walking  or  swim- 
ming, and  which  in  some  extinct  forms  support  a  flying  mem- 
brane. The  internal  skeleton  is  always  bony,  never  cartila- 
ginous or  semi-cartilaginous  as  in  many  of  the  fishes.  The 
skull  is  joined  to  the  spine  by  a  single  articulating  surface  (or 
condyle).  The  lower  jaw  is  complex,  each  half  being  com- 
posed of  several  pieces  united  by  sutures.  In  Tortoises  and 
Turtles,  however,  these  separate  pieces  are  amalgamated  to- 
gether, and  the  two  halves  are  also  united,  so  that  the  whole 
lower  jaw  appears  to  form  a  single  piece.  In  most  Reptiles, 
on  the  other  hand,  the  two  halves  of  the  lower  jaw  (Fig.  116) 
are  only  loosely  united ;  in  the  Snakes  by  ligaments  and  mus- 
cles, in  the  Lizards  by  gristle,  and  in  the  Crocodiles  by  suture. 


FIG.  116.— Skull  of  a  Serpent  (Python),    a  Quadrate  bone ;  &  Lower  jaw,  articulating  with 
the  movable  quadrate  bone. 

In  all,  the  lower  jaw  is  jointed  to  the  skull  by  means  of  a 
special  bone,  called  the  "  quadrate  bone ; "  and  as  this  often 
projects  backward,  the  opening  of  the  mouth  is  often  very 
extensive,  and  may  even  extend  backward  beyond  the  base  of 
the  skull  (Fig.  116,  a).  Teeth  are  generally  present,  but  these 
are  used  chiefly  to  hold  the  prey,  and  not  in  biting  or  chewing 


236  VERTEBRATE  ANIMALS. 

the  food.  Except  in  the  Crocodiles,  the  teeth  are  not  sunk 
into  distinct  sockets,  and  they  are  usually  replaced  as  fast  as 
shed.  They  likewise  do  not  differ  from  one  another  sufficient- 
ly in  form  or  function  as  to  allow  of  their  being  divided  into 
different  sets,  as  they  can  be  in  the  Mammals.  Usually  the 
teeth  are  confined  to  the  jaws  proper,  but  in  some  cases  they 
are  carried  by  other  bones  of  the  mouth.  In  the  Tortoises 
and  Turtles  there  are  no  teeth,  and  the  jaws  are  simply 
sheathed  in  horn,  so  as  to  constitute  a  kind  of  beak,  like  that 
of  a  bird.  The  integumentary  skeleton  is  in  the  form  of 
scales,  sometimes  combined  with  bony  plates.  In  the  Tor- 
toises and  Turtles  the  integumentary  skeleton  is  so  united 
with  the  true  skeleton  as  to  form  a  kind  of  bony  case  or  box, 
in  which  the  body  is  enclosed. 

The  digestive  system  presents  little  worthy  of  special  no- 
tice, except  that  the  termination  of  the  intestine  (rectum)  opens 
into  a  cavity  called  the  "  cloaca,"  which  receives  also  the  ducts 
of  the  urinary  and  generative  organs. 

It  is,  however,  in  the  structure  of  the  circulatory  and  respir- 
atory organs  that  the  most  important  characters  of  the  Reptiles 
are  to  be  looked  for.  The  heart  in  all  Reptiles  may  be  regarded 
as  being,  in  function^  three-chambered,  being  composed  of  two 
auricles  and  a  single  ventricle,  imperfectly  divided  by  an  in- 
complete partition.  In  the  Crocodiles  alone  the  heart  is,  struct- 
urally, four-chambered,  the  ventricle  being  divided  into  two 
by  a  complete  partition.  Here,  however,  the  same  results  are 
brought  about  as  in  the  other  Reptiles,  by  means  of  a  commu- 
nication which  subsists  between  the  great  vessels  which  spring 
from  the  ventricles  thus  formed.  In  the  ordinary  Reptiles  the 
course  of  the  circulation  is  as  follows  (Fig.  117) :  The  impure 
or  venous  blood  that  has  circulated  through  the  body  is  poured 
by  the  great  veins  into  the  right  auricle  (a).  The  pure  or 
arterial  blood  that  has  been  submitted  to  the  action  of  the 
lungs  is  poured  by  the  pulmonary  veins  into  the  left  auricle 
(a1).  Both  auricles  empty  their  contents  into  the  ventricle, 
and,  as  the  partition  which  divides  the  ventricle  is  an  incom- 
plete one,  it  follows  that  the  venous  and  arterial  streams  must 
mix  to  a  greater  or  less  extent  in  the  ventricle.  From  the 
ventricle  arise  the  great  vessels  which  carry  the  blood  to  the 
lungs  and  to  all  parts  of  the  body,  and  it  follows,  as  a  matter 
of  necessity,  that  all  these  parts  are  supplied  with  a  mixed 
fluid,  consisting  partly  of  impure  or  venous  blood,  and  partly 
of  pure  or  arterial  blood.  In  the  Crocodiles,  in  which  there 
are  two  ventricles  completely  separated  from  each  other,  the 


REPTILIA. 


237 


same  result  is  brought  about  by  means  of  a  communication 
which  takes   place  between  the  great  vessels  which  spring 
from  the  ventricles,  in  the  imme- 
diate neighborhood  of  the  heart. 

From  this  brief  description  it 
will  be  seen  that  the  peculiarity 
of  the  circulation  in  Reptiles  con- 
sists in  the  fact,  that  the  lungs 
and  all  parts  of  the  body  are  sup- 
plied with  mixed  blood ;  whereas 
in  the  higher  Vertebrates  the 
lungs  are  supplied  with  pure 
venous  blood,  and  the  various  tis- 
sues of  the  body  with  pure  arte- 
rial blood. 

As  regards  the  structure  of 
the  lungs,  it  is  merely  to  be  noted 
that  there  is  no  partition  (dia- 
phragm or  midriff)  separating 
the  two  cavities  of  the  thorax  and 
abdomen,  and  that  the  lungs, 
therefore,  often  attain  a  great  pro- 
portionate size,  sometimes  ex- 
tending through  almost  the  whole 
length  of  the  cavity  of  the  trunk. 
There  are  also  no  air-sacs  commu- 
nicating  with  the  lungs,  as  in  the 
Birds. 

Lastly,  all  Reptiles  are  essen- 
tially oviparous,  some  being  ovo- 
viviparous.  The  egg-shell  is  usu- 
ally parchment-like,  but  in  other 
cases  contains  more  or  less  cal- 
careous matter. 

The  class  Reptilia  is  divided  into  four  living  and  five  ex- 
tinct orders,  as  follows,  but  the  latter  require  but  brief  notice : 

1.  Chelonia  (Tortoises  and  Turtles). 

2.  Ophidia  (Snakes). 

3.  Lacertilia  (Lizards). 

4.  Crocodilia  (Crocodiles). 

5.  Ichthyopterygia  1 

6.  Sauropterygia 

7.  Pterosauria          V  Extinct. 

8.  Anomodontia 

9.  Deinosauria 


venous  blood  from  the  body ;  a'  Left 
auricle,  receiving  arterial  blood  from 
the  lungs;  v  Arterio-venous  ventri- 
cle, containing  mixed  blood,  which  is 
driven  by  (p)  the  pulmonary  artery  to 
the  lungs,  and  by  (0)  the  aorta  to  the 
body.  (The  venous  system  is  left  light, 
the  arterial  system  is  black,  and  the 
vessels  containing  mixed  blood  are 
cross-shaded.) 


CHAPTER  XXVIII. 
DIVISIONS    OF    REPTILIA. 

ORDER  I.  CHELONIA  (Gr.  chelone,  a  tortoise). — In  this 
order  are  included  the  various  Tortoises  and  Turtles,  charac- 
terized by  having  the  body  enclosed  in  a  bony  case  or  box, 
and  by  the  fact  that  the  jaws  are  not  provided  with  teeth,  but 
are  encased  in  horn,  so  as  to  form  a  kind  of  beak.  The  case 
in  which  the  body  of  a  Chelonian  is  protected  is  composed 
partly  of  integumentary  plates,  and  partly  of  flattened  bones 
belonging  to  the  true  skeleton,  and  it  is  composed  essentially 
of  two  pieces,  one  placed  on  the  back  and  the  other  on  the 
lower  surface  of  the  body,  firmly  united  together  at  their  edges. 
The  dorsal  shield  is  more  or  less  convex  and  rounded,  and  is 
called  the  carapace  (Fig.  118,  ca) ;  while  the  ventral  shield  is 
more  or  less  completely  flat  or  concave,  and  is  called  the  plas- 
tron. The  carapace  and  plastron,  as  just  said,  are  united  by 
their  edges,  but  they  leave  two  openings,  one  in  front  for  the 
head,  and  one  behind  for  the  tail.  The  carapace  is  essentially 
composed  of  the  flattened  and  expanded  spinous  processes  of 
the  vertebrae  and  the  greatly-developed  ribs,  covered  by  a 
series  of  horny  plates.  These  are  growths  of  the  integument, 
and  in  some  cases  they  constitute  the  "  tortoise-shell "  of  com- 
merce. The  plastron  is  also  composed  partly  of  bony  and 
partly  of  horny  plates,  but  opinions  differ  as  to  whether  the 
bony  plates  are  to  be  looked  upon  as  formed  by  an  expanded 
breastbone,  or  whether  they  are  merely  integumentary,  the 
probabilities  being  in  favor  of  the  latter  view. 

The  remaining  peculiarities  with  regard  to  the  skeleton 
which  deserve  special  mention  are :  Firstly,  that  the  dorsal 
vertebrae  are  immovably  connected  together,  so  that  this  region 
of  the  spine  is  quite  inflexible ;  secondly,  that  the  heads  of  the 
ribs  are  articulated  directly  to  the  bodies  of  the  vertebrae ;  and, 


DIVISIONS  OF  REPTILIA. 


239 


thirdly,  that  the  scapular  and  pelvic  arches,  supporting  respec- 
tively the  fore  and  hind  limbs,  are  situated  within  the  carapace 
(Fig.  118,  s  and  p\  so  that  the  shoulder-blade  is  placed  inside 
the  ribs  instead  of  outside,  as  is  usually  the  case. 


FIG.  118.— Skeleton  of  a  Tortoise  (Emys  Ewropaia\  seen  from  below,  the  plastron  having: 
been  removed,  ca  Carapace,  showing1  the  flattened  and  expanded  ribs ;  s  Scapular 
arch,  carrying  the  fore-limbs,  and  placed  in  the  interior  of  the  carapace ;  p  Pelvic  arch, 
carrying  the  hind-limbs ;  r  Kibs. 

The  Chelonia  are  conveniently  divided  into  groups,  accord- 
ing as  the  limbs  are  adapted  for  swimming  (natatory),  or  for 
progression  on  land  (terrestrial) ;  or,  again,  enable  the  animal 
to  lead  an  amphibious  life,  sometimes  on  land  and  sometimes 
in  the  water.  Of  the  strictly  aquatic  forms  the  best  known 
are  the  edible  Green  Turtle  (  Chelonia  midas)  and  the  Hawk's- 
bill  Turtle  ( Chelonia  imbricata).  The  former  is  found  abun- 
dantly in  many  of  the  seas  of  warm  climates,  and  is  largely 
imported  into  Europe  as  a  delicacy.  The  latter  (Fig.  119)  is 
truly  a  native  of  warm  seas,  though  an  occasional  straggler 
has  reached  the  shores  of  Britain.  It  is  of  comparatively 
small  size — not  more  than  about  three  feet  in  length — but  is 


240  VERTEBRATE  ANIMALS. 

of  considerable  commercial  importance,  as  it  furnishes  the 
"  tortoise-shell "  of  trade,  so  largely  used  in  various  kinds  of 
ornamental  work. 


FIG.  119.— The  Hawk-billed  Turtle  (CJwlonia  imbricata).    (After  Bell.) 

The  Sea-tortoises  or  Turtles  have  the  carapace  much  flat- 
tened, the  legs  of  unequal  length,  in  the  form  of  solid  fins  or 
oars,  the  toes  being  conjoined,  and  hardly  distinct  from  one 
another. 

The  Marsh,  Pond,  and  River  Tortoises  are  generally  fur- 
nished with  webbed  feet,  and  lead  an  amphibious,  semi-aquatic 
existence.  The  so-called  "  Soft  Tortoises  "  (Trionycidce]  be- 
long here,  and  are  distinguished  by  the  imperfect  condition 
of  the  carapace,  which  is  simply  covered  with  a  leathery  skin. 
A  good  example  is  the  Soft-shelled  Turtle  (T.ferox)  of  the 
Southern  States.  Here  also  belong  the  Snapping-turtles,  so 
well  known  in  the  person  of  the  common  American  species 
(Chetydra  serpentina),  and  the  Terrapins  (Emydidce),  of 
which  many  forms  are  found  in  all  parts  of  the  United  States. 
In  the  curious  little  Box-tortoise  ( Cistudo  Virgined)  the  plas- 
tron is  composed  of  two  movable  portions  which  can  be 
brought  into  accurate  apposition  with  the  carapace,  thus  com- 
pletely protecting  the  animal  within. 

The  Land  Tortoises  have  short  legs  of  nearly  equal  length, 
the  toes  little  distinct,  and  united  into  a  sort  of  stump,  with 
indistinct,  horny  claws.  Good  examples  of  this  group  are  the 


DIVISIONS  OF  REPTILIA.  241 

common  European  Tortoise  (Testudo  Grceca)  and  the  Indian 
Tortoise  (T.  Indica),  the  last  attaining  a  length  of  over  three 
feet. 

ORDER  II.  OPHIDIA  (Gr.  ophis,  a  serpent). — This  order  in- 
cludes most  of  the  animals  which  would  commonly  be  called 
snakes  or  serpents,  and  is  characterized  by  the  following  pecu- 
liarities :  The  body  is  always  more  or  less  elongated,  worm- 
like  or  cylindrical,  and  the  skin  develops  horny  scales,  but 
never  bony  plates.  There  is  never  any  breastbone  (sternum), 
nor  pectoral  arch,  nor  fore-limbs ;  nor,  as  a  rule,  are  there  any 
traces  of  hind-limbs.  In  a  few  cases,  however,  rudimentary 
hind-limbs  can  be  detected.  The  ribs  are  always  very  numer- 
ous. The  two  halves  of  the  lower  jaw  are  composed  of  several 
pieces  each,  and  they  are  united  to  one  another  in  front  only 
by  ligaments  and  muscles  (Fig.  120).  Hooked,  conical  teeth 


FIG.  120.— The  Naja  Hqje,  a  poisonous  Snake  of  Egypt. 

are  always  present,  but  they  are  never  lodged  in  distinct 
•sockets,  and  are  only  used  to  hold  the  prey,  and  not  in  masti- 
cation. The  lungs  and  other  paired  organs  are  often  not  sym- 
metrical, one  of  each  pair  being  usually  smaller  than  the  other, 
or  altogether  absent. 


242  VERTEBRATE  ANIMALS. 

The  most  striking  of  these  characters  of  the  snakes  is  to 
be  found  in  the  nature  of  the  organs  of  locomotion.  The 
fore-limbs  are  invariably  altogether  wanting,  and  there  is  no 
pectoral  arch  nor  breastbone ;  and  the  hind-limbs  are  either 
totally  absent  or  are  at  best  rudimentary  and  never  exhibit 
any  outward  evidence  of  their  existence,  beyond  the  occasion- 
al presence  of  short,  horny  claws  or  spurs.  In  the  entire  ab- 
sence, then,  or  rudimentary  condition  of  the  limbs,  the  snakes 
progress  by  means  of  the  ribs,  which  are  always  excessively 
numerous,  and,  in  the  absence  of  a  breastbone,  are  also  ex- 
tremely movable.  Their  free  ends,  in  fact,  are  simply  attached 
by  muscular  fibres  to  the  scales  or  "  scutes,"  which  cover  the 
lower  or  abdominal  surface  of  the  animal.  The  number  of 
ribs  varies  from  50  up  to  320  pairs,  and,  by  means  of  this 
arrangement,  the  snakes  are  able  to  progress  rapidly,  walking, 
as  it  were,  upon  the  ends  of  the  ribs.  Their  movements  are 
also  much  assisted  by  the  extreme  flexibility  of  the  whole 
spine,  caused  by  the  cup-and-ball  articulation  of  the  bodies  of 
the  vertebrae,  each  of  which  is  concave  in  front  and  convex 
behind  (proccelous). 

Of  the  other  characters  of  the  snakes,  a  few  words  may  be 
said  as  to  the  tongue,  the  eye,  and  the  teeth — all  important 
structures  in  this  order.  The  tongue,  in  serpents,  is  probably 
more  an  organ  of  touch  than  of  taste,  and  consists  of  two 
muscular  cylinders,  which  are  united  toward  their  bases.  The 
forked  organ  thus  formed  can  be  protruded  and  retracted  at 
will,  being  in  constant  vibration  when  protruded,  and  being 
in  great  part  concealed  by  a  sheath  when  retracted.  The  eye 
of  serpents  (Fig.  121,  A)  is  not  protected  by  any  eyelids,  and 
hence  the  peculiar  stony  and  unwinking  stare  for  which  these 
reptiles  are  celebrated.  In  place  of  eyelids,  the  outer  layer 
of  the  skin  is  prolonged  over  the  eye  as  a  continuous  and 
transparent  film,  behind  which  is  a  chamber  formed  by  the 
mucous  covering  of  the  eye,  into  which  the  tears  are  dis- 
charged. The  outer  membrane  is  periodically  shed  along  with 
the  rest  of  the  external  or  epidermic  layer  of  the  integument, 
and  is  again  renewed.  The  pupil  is  round  in  most  serpents, 
but  it  forms  a  vertical  slit  or  fissure  in  the  venomous  snakes 
and  in  the  Boas. 

As  regards  the  teeth,  it  is  to  be  noticed  that  the  snakes 
are  not  in  the  habit  of  chewing  their  prey,  but  of  swallowing- 
it  whole,  and  the  construction  of  their  dental  apparatus  is  in 
accordance  with  this  peculiarity.  The  lower  jaw,  as  before 
said,  articulates  with  the  skull  by  means  of  a  quadrate  bone 


DIVISIONS   OF  REPTILIA. 


243 


(Fig.  117),  and  this  in  turn  is  movably  jointed  to  the  cranium. 
The  two  halves  of  the  lower  jaw  are  also  merely  united 
loosely  in  front  by  ligaments  and  muscles.  In  consequence 
of  this  peculiar  arrangement  of  parts,  the  serpents  have  the 
power  of  opening  the  mouth  to  an  extraordinary  width,  and 
they  can  perform  the  most  astonishing  feats  in  the  way  of 
swallowing.  The  teeth  are  simply  fitted  for  seizing  and  hold- 
ing the  prey,  but  not  in  any  way  for  chewing  or  dividing  it. 
In  the  harmless  snakes,  the  teeth  are  in  the  form  of  solid 
cones,  which  are  arranged  in  rows  round  the  whole  of  the 
upper  and  lower  jaws,  a  double  row  existing  on  the  palate 
as  well.  In  the  venomous  snakes,  on  the  other  hand,  the 
ordinary  teeth  are  usually  wanting  upon  the  upper  jaws,  and 
these  bones  are  themselves  much  reduced  in  size.  In  place 
of  the  ordinary  teeth,  however,  the  upper  jaws  carry  the  so- 
called  "j>oison-fangs  "  (Fig  121,  B).  These  are  a  pair  of  long, 


FIG.  121.— A,  Diagrammatic  Section  of  the  Eye  of  a  Viper  (after  Cloquet).  a  Eyeball;  6 
Optic  nerve ;  c  Chamber  into  which  the  tears  are  poured ;  d  Epidermic  layer  covering 
the  eye.  B,  Head  of  the  common  Viper  (after  Bell),  showing  the  poison-fangs. 

curved  fangs,  one  on  each  maxilla  or  upper  jawbone,  which, 
when  not  in  use,  are  pointed  backward,  and  concealed  in  a 
fold  of  the  gum,  but  can  be  raised  at  will  by  special  muscles. 
Each  tooth  is  perforated  by  a  fine  canal  or  tube,  which  opens 
by  a  distinct  aperture  at  the  point  of  the  fang,  and  is  connect- 
ed with  the  duct  of  the  "  poison-gland."  This  is  a  gland, 
situated  under  and  behind  the  eye,  secreting  the  poisonous 
fluid  which  renders  the  bites  of  these  snakes  dangerous  or 
fatal.  When  the  serpent  strikes  at  any  animal,  the  poison  is 
forced  through  the  poison-fang  into  the  wound,  partly  by  the 
contractions  of  the  muscular  walls  of  the  gland,  and  partly  by 
the  compressive  action  of  the  muscles  of  the  jaws.  In  some 
other  snakes,  several  of  which  are  not  certainly  known  to  be 


244  VERTEBRATE  ANIMALS. 

venomous,  there  are  large,  grooved  fangs  placed  far  back  in 
the  mouth  upon  the  upper  jaw. 

Of  the  non-venomous,  harmless  snakes,  we  have  an  excel- 
lent instance  in  the  common  Ringed  Snake  (Coluber  natrix), 
which  is  of  frequent  occurrence  in  most  parts  of  Europe. 
Like  all  the  snakes,  it  is  strictly  carnivorous,  having  a  special 
liking  for  frogs,  which  it  swallows  whole.  It  often  takes  to 
the  water,  and  can  swim  rapidly  and  gracefully,  though,  in 
this  respect,  it  is  excelled  by  the  true  venomous  water-snakes 
(Hydrophidce),  which  are  adapted  to  an  aquatic  life  by  having 
a  compressed  swimming- tail.  A  well-known  American  exam- 
ple of  this  group  is  the  common  Black  Snake  (Bascanion 
constrictor).  It  attains  a  length  of  from  three  to  five  feet,  but 
is  perfectly  harmless  so  far  as  man  is  concerned.  Other  non- 
venomous  snakes,  such  as  the  Boas  and  Pythons,  though  des- 
titute of  poison-fangs,  are,  nevertheless,  highly  dangerous  and 
destructive  animals.  Their  bite  is  harmless,  and  they  seize 
their  prey  by  coiling  themselves  round  it  in  numerous  folds. 
By  gradually  tightening  these  folds,  they  reduce  their  victim 
to  the  condition  of  a  shapeless  bolus,  which  they  finally  pro- 
ceed to  swallow  whole.  In  this  way,  a  large  Python  or  Boa 
will  certainly  succeed  in  disposing  of  an  animal  as  large  as  a 
sheep  or  calf,  and  it  has  been  asserted  that  human  beings, 
and  even  oxen,  can  also  be  swallowed  by  unusually  large 
specimens  of  this  family. 

The  Boas  and  Pythons  have  a  horny  spur  on  each  side  of 
the  vent,  and  the  tail  is  prehensile.  Their  dental  apparatus  is 
extremely  powerful,  giving  them  a  firm  hold  for  the  constric- 
tion of  their  prey.  They  are  the  largest  of  all  the  serpents, 
attaining  a  length  of  thirty  to  forty  feet.  The  true  Boas 
and  Anacondas  belong  to  the  New  World,  but  the  Pythons 
are  confined  to  India,  Africa,  and  the  Indian  Archipelago. 

The  poisonous  snakes  are  represented  by  the  Crotalidce 
of  the  New  World  and  the  Viperidce  of  the  Old  World.  The 
common  Rattlesnake  ( Crotalus  horridus)  of  the  United  States 
has  the  extremity  of  the  tail  furnished  with  a  "  rattle "  or 
horny  appendage  composed  of  several  membranous  cells  of  a 
pyramidal  shape  articulated  one  within  the  other.  Before 
striking  its  prey,  it  throws  itself  into  a  coil,  and  shakes  its 
rattle.  Another  highly-dangerous  species  is  the  Copperhead 
(Trigonocephalus  contortrix).  The  common  European  viper 
(Pelias  berus)  is  hardly  fatal  to  adults,  but  its  bite  causes 
serious  inflammation.  Highly  deadly,  however,  is  the  Cobra 
di  Capello  or  Spectacled  Snake  (JVaja  trijncdians)  of  India,  as 


DIVISIONS  OF  EEPTILIA.  245 

also  is  the  nearly-allied  JVaja  haje  (Fig.  120)  of  Africa.  Oth- 
er venomous  snakes  of  evil  notoriety  are  the  Death-adder 
(Acanthophis  tort  or)  of  Australia,  the  Puff-adder  (  Viper  a  in- 
flatd)  of  South  Africa,  the  Horned  Viper  ( Cerastes  cornutus] 
of  Egypt,  and  the  Harlequin-snakes  (JElaps),  but  many  others 
are  equally  dangerous. 

OEDEK  III.  LACEETILIA  (Lat.  lacerta,  a  lizard). — The  third 
order  of  reptiles  is  that  of  the  Lacertilia,  comprising  all  the  ani- 
mals which  are  properly  known  as  Lizards,  together  with  some 
snake-like  creatures,  such  as  the  Blind-worm.  They  are  distin- 
guished by  the  following  characters :  Usually  there  are  two  pairs 
of  well-developed  limbs,  but  there  may  be  only  one  pair,  or  all  the 
limbs  may  be  rudimentary.  In  all  cases,  however,  a  scapular 
arch  is  present.  The  vertebrae  are  usually  hollow  in  front 
(procoelous) ,  rarely  hollow  at  both  ends  (amphicoelous).  In  no 
living  Lacertilian  are  the  teeth  lodged  in  distinct  sockets. 
The  eyes  are  mostly  furnished  with  movable  eyelids. 

As  a  general  rule,  the  animals  included  under  this  head 
have  four  well-developed  legs,  and  would,  therefore,  be  popu- 
larly called  "  Lizards."  Some  of  them,  however,  such  as  the 
common  Blind-worm  (Anguis  fragilis)  of  Europe,  exhibit  no 
external  indications  of  limbs,  and  would,  therefore,  be  generally 
regarded  as  Snakes.  These  snake-like  Lizards,  however,  can 
be  distinguished  from  the  true  Ophidians  by  the  consolidation 
of  the  bones  of  the  head  and  jaws,  and  by  the  fact  that  the 
eyes  are  generally  provided  with  movable  eyelids.  Dissection 
also  shows  that  the  shoulder-girdle  (or  scapular  arch)  is  always 
present  in  a  rudimentary  condition. 

Of  the  snake-like  Lizards,  a  good  example  is  to  be  found 
in  the  common  Blind-worm  or  Slow-worm  of  Europe.  It  is 
completely  serpentiform,  without  any  external  indications  of 
limbs  (Fig.  122),  and  it  is  quite  harmless.  It  is  remarkable 
for  the  fact  that,  when  alarmed,  it  stiffens  its  muscles  to  such 
an  extent  that  the  tail  can  readily  be  broken  off,  as  if  it  were 
brittle.  This  same  brittleness  exists  in  the  Glass-snake  ( Ophi- 
saurus  ventralis)  of  the  Southern  States,  in  which  also  there 
are  no  limbs.  In  other  allied  genera,  there  may  be  fore-feet 
alone,  or  hind-feet  may  be  present,  or  all  four  limbs  exist  in  a 
more  or  less  rudimentary  condition.  In  the  true  Lizards 
(Lacerta\  all  four  limbs  are  present  in  a  well-developed  form ; 
as  seen  in  the  common  Green  Lizard  (J£.  viridis)  of  Europe. 
The  genus  Lacerta  is  represented  in  America  by  the  Ameivce,  of 
which  the  Striped  Lizard  (Ameiva  sex-lineatd)  of  the  Southern 


246  VERTEBRATE  ANIMALS. 

States  may  be  taken  as  a  good  example.  Of  all  living  Lizards, 
the  largest  are  the  Monitors  ( Varanidoe^)  which  are  exclusively 
confined  to  the  Old  World,  and  attain  sometimes  a  length  of 
from  six  to  eight  feet.  Very  large,  too,  are  some  of  the 


FIG.  122.— Blind-worm  (Anguis  fragilis).    (After  BclL) 

Iguanas  which  occur  in  warm  regions  in  various  parts  of 
the  world,  but  especially  in  South  America,  where  they  are 
often  eaten.  Related  to  the  Iguanas  are  the  singular  Lizards 
known  as  the  Flying  Dragons  (Draco  volans),  various  species 
of  which  inhabit  the  Indian  Archipelago  and  the  East  Indies. 
They  are  all  of  small  size,  living  in  trees  and  feeding  on  in- 
sects ;  and  their  great  peculiarity  consists  in  the  fact  that  cer- 
tain of  the  ribs  are  straightened  out,  and  support  a  wing-like 
fold  of  the  skin  on  each  side  of  the  body,  by  means  of  which 
the  animal  can  take  very  extensive  leaps  from  tree  to  tree. 

The  Scincoid  Lizards  form  a  very  large  family,  represented 
by  numerous  species  in  all  parts  of  the  world.  The  species 
figured  below  is  a  common  form  in  Egypt  and  Arabia,  and  was 
formerly  used  as  a  remedy  in  various  diseases.  A  nearly- 
allied  species  is  the  Blue-tailed  Lizard  (Scincus  fasciatus)  of 
the  United  States. 

The  Geckos  ( GeckotidoB]  form  a  large  group  of  night-lov- 
ing Lizards,  which  are  found  in  most  parts  of  the  world,  and 


DIVISIONS   OF  KEPTILIA. 


247 


chiefly  deserve  notice  from  the  fact  that  their  eyes  are  not  pro- 
vided with  movable  eyelids.  The  Chameleons,  also,  cannot 
be  said  to  possess  movable  eyelids,  for  the  eye  is  covered  with 


FIG.  123.— The  Skink  (ScincuxofficinaUz) 


a  single  lid,  leaving  only  a  central  aperture  for  the  pupil.  The 
common  species  ( Chameleo  Africanus)  occurs  abundantly  in 
the  north  of  Africa,  and  has  long  been  known  for  the  changes 
of  color  which  it  has  the  power  of  exhibiting.  It  is  a  sluggish 
animal,  and  catches  insects  by  darting  out  its  long  and  pro- 
trusible  tongue  with  extreme  rapidity. 

ORDER  IV.  CROCODILIA. — The  last  and  highest  order  of 
the  living  Reptiles  is  that  of  the  Crocodilia,  comprising  the 
Crocodiles,  Alligators,  and  Gavials,  and  characterized  by  the 
following  peculiarities :  The  outer  or  integumentary  skeleton 
consists  partly  of  horny  scales  developed  by  the  outer  layer 
of  the  skin,  and  partly  of  large  bony  plates  produced  by  the 
inner  layer  of  the  skin.  The  bones  of  the  skull  and  face  are 
firmly  united,  and  the  two  halves  of  the  lower  jaw  are  joined 
by  a  distinct  suture.  The  teeth  form  a  single  row  in  both 
jaws,  and  are  implanted  in  distinct  and  separate  sockets.  The 
front  ribs  of  the  trunk  are  double-headed,  and  there  are  no 
collar-bones.  The  heart  consists  of  four  distinct  chambers, 
two  auricles  and  two  ventricles,  all  completely  separated  from 


248  VERTEBRATE  ANIMALS. 

one  another.  The  mixture  of  arterial  and  venous  blood,  how- 
ever, which  is  so  characteristic  of  Reptiles,  is  provided  for  by 
a  communication  between  the  great  vessels  which  spring  from 
the  two  ventricles  in  the  immediate  neighborhood  of  the  heart. 
The  eyes  are  protected  by  movable  eyelids,  and  the  ear  by  a 
movable  earlid.  The  tongue  is  large  and  fleshy,  and  is  im- 
movably attached  to  the  bottom  of  the  mouth  (hence  the  be- 
lief of  the  ancients  that  the  Crocodile  had  no  tongue).  Lastly, 
the  Crocodilia  agree  with  the  typical  Lizards,  and  differ  from 
the  Snakes  in  having  four  well-developed  limbs. 


FIG.  124. — Head  and  fore-part  of  the  body  of  the  common  Crocodile  (Crocodilus  vulgaris). 

The  Crocodilia  abound  in  the  fresh  waters  of  hot  climates, 
and  are  the  largest  of  all  living  Reptiles,  not  uncommonly  at- 
taining a  length  of  sixteen  feet  or  upward.  The  best  known 
of  the  Crocodilia  is  the  Nilotic  Crocodile,  which  occurs  abun- 
dantly in  Egypt,  and  was  described  by  both  Herodotus  and 
Aristotle. 

The  true  Crocodiles  have  the  feet  completely  webbed,  the 
hind-legs  bordered  by  a  fringe,  and  the  fourth  tooth  in  the 
lower  jaw  received  in  a  notch  on  the  side  of  the  upper  jaw. 
They  belong  mainly  to  Africa  and  Asia,  but  they  are  also  rep- 
resented in  the  West  Indies  and  in  South  America. 

The  Alligators  have  the  hind-legs  simply  rounded,  and  the 
toes  not  completely  webbed ;  while  the  fourth  tooth  in  the 
lower  jaw  fits  into  a  cavity  in  the  palate,  and  is  concealed 
from  view  when  the  mouth  is  shut.  Like  the  Crocodiles  they 
are  essentially  aquatic  in  their  habits,  and  lie  dormant  during 
the  winter  in  cold  climates  and  the  hot  season  in  warm  coun- 
tries. They  are  extremely  voracious,  and  live  upon  fish  and 
small  Mammals.  The  best-known  species  are  the  common 
Alligator  (A.  Mississippiensis)  of  the  Southern  States,  the 
Caiman  (A.  palpebrosus)  of  Surinam  and  Guiana,  and  the 
"  Jacare1 "  (A.  sclerops)  of  South  America. 

The  Gavial  or  Gangetic  Crocodile  occurs  in  India,  and  is 


DIVISIONS  OF  REPTILIA.  249 

distinguished  by  its  narrow,  elongated  jaws,  forming  a  kind 
of  beak.     It  attains  a  length  of  more  than  ten  feet. 

OKDER  V.  ICHTHYOPTEEYGIA  (Gr.  ichthus,  fish ;  pterux, 
wing). — In  this  order  are  included  a  number  of  gigantic,  fish- 
like  Reptiles,  which  are  all  extinct,  and  are  characteristic  of 
the  Secondary  period  of  geology,  and  especially  of  the  forma- 
tion known  as  the  Lias.  The  chief  characters  by  which  they 
are  distinguished  have  reference  to  their  purely  aquatic  life, 
for  there  can  be  no  doubt  that  they  were  inhabitants  of  the 
sea.  Thus  the  body  was  fish-like,  without  any  distinct  neck. 
The  vertebras  were  hollow  at  both  ends  (amphiccelous) ,  and 
the  spine  thus  possessed  the  flexibility  and  power  of  motion 
so  characteristic  of  the  true  fishes.  The  limbs  also  consti- 
tuted powerful  swimming-paddles  (Fig.  125),  and  it  is  proba- 
ble that  there  was  a  vertical  tail-fin. 

Much  has  been  gathered  from  various  sources  as  to  the 
habits  of  the  Ichthyosauri,  and  their  history  is  one  of  the  most 
interesting  chapters  in  the  geological  record.  That  they 
chiefly  kept  to  open  seas  may  be  inferred  from  their  strong 
and  well-developed  swimming  apparatus ;  but  the  presence  of 
a  powerful  bony  arch  supporting  the  fore-limbs  proves  that 


FIG.  125. — Ichthyosaurus  communte. 

they  must  have  occasionally  betaken  themselves  to  the  land. 
That  they  were  tenants  of  stormy  waters,  or  were  in  the  habit 
of  diving  in  search  of 'prey,  has  been  inferred  from  the  fact 
that  the  eyeball  is  protected  from  pressure  by  a  ring  of  bony 
plates.  That  they  possessed  great  powers  of  vision,  espe- 
cially in  the  dusk,  seems  to  be  rendered  certain  from  the  size 
of  the  pupil  and  the  enormous  width  of  the  bony  cavities 
(orbits)  which  contained  the  eyes.  Lastly,  that  they  were 
carnivorous  and  predacious  in  the  highest  degree  is  shown  by 
their  wide  mouths,  long  jaws,  and  numerous  powerful  and 
pointed  teeth.  This  is  also  proved  by  an  examination  of  their 
petrified  droppings,  which  are  known  as  "  coprolites,"  and 
which  contain  in  abundance  undigested  fragments  of  fishes 
and  other  marine  animals. 


250  VERTEBRATE  ANIMALS. 

ORDER  VI.  SAUROPTERYGIA  (Gr.  saura,  lizard ;  pterux, 
wing). — The  Reptiles  belonging  to  this  order  agree  with  the 
last  in  being  all  extinct,  and  in  being  confined  to  the  Second- 
ary period  of  geology.  The  best  known  are  the  Plesiosauri, 
which  resembled  the  Ichthyosauri  in  having  all  the  limbs  con- 
verted into  swimming-paddles,  but  differed  in  several  respects, 
of  which  the  most  obvious  is  the  great  elongation  of  the  neck 
(Fig.  126).  The  Plesiosauri  were  gigantic  marine  Reptiles, 


FIG.  126.— Plesiosaurus  dolichodwrus. 

chiefly  characteristic  of  the  formations  known  as  the  Lias  and 
Oolites.  As  regards  the  habits  of  the  Plesiosaurus,  Dr.  Cony- 
beare  concludes  :  "  That  it  was  aquatic  is  evident  from  the  form 
of  its  paddles ;  that  it  was  marine  is  almost  equally  so  from  the 
remains  with  which  it  is  universally  associated ;  that  it  may 
have  occasionally  visited  the  shore,  the  resemblance  of  its  ex- 
tremities to  those  of  the  Turtle  may  lead  us  to  conjecture ;  its 
movements,  however,  must  have  been  very  awkward  on  land : 
and  its  long  neck  must  have  impeded  its  progress  through  the 
water,  presenting  a  striking  contrast  to  the  organization 
which  so  admirably  fits  the  Ichthyosaurus  to  cut  through  the 
waves."  As  its  breathing-organs  are  such  that  it  must  of  ne- 
cessity have  required  to  obtain  air  frequently,  it  may  be  in- 
ferred "  that  it  swam  upon  or  near  the  surface,  arching  back 
its  long  neck  like  a  swan,  and  occasionally  darting  it  down  at 
the  fish  which  happened  to  float  within  its  reach.  It  may  per- 
haps have  lurked  in  shoal-water  along  the  coast,  concealed 
among  the  sea-weed,  and,  raising  its  nostrils  to  a  level  with 
the  surface  from  a  considerable  depth,  may  have  found  a  se- 
cure retreat  from  the  assaults  of  powerful  enemies ;  while  the 
length  and  flexibility  of  its  neck  may  have  compensated  for 
the  want  of  strength  in  its  jaws  and  its  incapacity  for  swift 
motion  through  the  water." 

ORDER  VII.  PTEROSATJRIA  (Gr.  pteron,  wing;  saura, 
lizard). — The  Reptiles  of  this  order  are  all  extinct,  and,  like 
those  of  the  preceding  orders,  are  exclusively  confined  to  the 


DIYISIONS  OF  REPT1LIA.  251 

Secondary  period  of  geology.  The  most  familiar  examples 
are  the  so-called  Pterodactyles,  and  the  distinguishing  charac- 
ters of  the  order  have  reference  to  the  fact  that  they  were  all 
adapted  for  an  aerial  life.  They  present,  in  fact,  an  extraor- 
dinary combination  of  the  characters  of  birds  and  reptiles,  and 
they  make  also  some  approach  to  the  Mammalian  order  of  the 
Bats.  In  the  presence  of  teeth  in  distinct  sockets,  and,  as  we 
shall  see  hereafter,  in  the  structure  of  the  fore-limbs,  the 
Pterodactyles  differ  altogether  from  all  known  birds ;  and 
there  can  be  little  doubt  as  to  their  being  genuine  Reptiles. 
The  only  living  Reptile  which  has  any  power  of  sustaining 
itself  in  the  air  is  the  little  Draco  volans,  which  has  been  pre- 
viously mentioned.  In  this  case,  however,  the  animal  has  no 
power  of  true  flight,  but  is  simply  enabled  to  take  extensive 
leaps  by  means  of  a  membranous  expansion  on  each  side  of 
the  body.  In  the  Bats,  again,  the  power  of  genuine  flight  is 
present ;  and  this  is  given  by  means  of  a  leathery  membrane 
which  is  supported  chiefly  by  certain  of  the  fingers — which 
are  greatly  lengthened — and  is  attached  to  the  sides  of  the 
body  and  hind-limbs. 

In  the  Pterodactyles  the  power  of  true  flight  was  present, 
and  this  was  also  conditioned  by  means  of  a  leathery  expand- 
ed membrane,  attached  to  the  hind-limbs,  the  sides  of  the 
body,  and  the  fore-limbs.  In  this  case,  however,  the  chief 
support  of  the  flying  membrane  was  derived  from  the  outer- 
most finger  of  the  fore-limb,  which  was  enormously  elongated 
(Fig.  127).  That  the  Pterodactyles  passed  their  existence 


FIG.  127. — Pterodactylus  br&virostris,  the  skeleton  and  the  animal  restored. 

chiefly  in  the  air,  and  did  not  simply  leap  from  tree  to  tree,  is 
shown  by  two  characters  in  which  they  agree  with  the  flying 


252  VERTEBRATE  ANIMALS. 

birds.  Many  of  the  bones,  namely,  were  "  pneumatic  " — that 
is  to  say,  were  hollow  and  were  filled  with  air,  thus  giving  the 
animal  the  degree  of  lightness  necessary  for  flight.  Secondly, 
while  the  shoulder-girdle  has  many  of  the  characters  of  birds, 
the  breastbone  (sternum)  is  furnished  with  a  prominent  ridge 
or  keel,  serving  for  the  attachment  of  the  great  muscles  which 
work  the  wings.  There  can  be  no  doubt,  therefore,  as  to  the 
Pterodactyles  having  enjoyed  the  power  of  genuine  flight. 
Many  of  them  attained  no  great  size,  but  some  of  them  must 
have  been  gigantic,  the  expanse  of  wing  in  one  species  having 
been  calculated  at  probably  about  twenty-seven  feet  from  tip 
to  tip. 

ORDER  VIII.  ANOMODONTIA  (Gr.  anomos,  irregular ; 
odous,  tooth). — This  order  comprises  a  few  Reptiles  which  be- 
long to  the  Triassic  period  of  geology,  and  are  distinguished 
by  the  fact  that  the  jaws  were  sheathed  in  horn,  so  as  to  form 
a  kind  of  beak  very  like  that  of  the  Turtles.  In  some  species 
there  appear  to  have  been  no  teeth  at  all ;  but  in  one  genus 
there  were  two  long  tusks,  one  on  each  side  of  the  upper  jaw. 
The  limbs  were  fitted  for  walking  and  not  for  swimming,  and 
these  singular  Reptiles  must,  therefore,  have  been  terrestrial 
in  their  habits. 

ORDER  IX.  DEINOSAURIA  (Gr.  demos,  terrible;  saura, 
lizard). — In  this  order  are  included  a  number  of  extinct  Rep- 
tiles, most  of  which  were  of  gigantic  size,  and  which  are  con- 
fined to  the  Secondary  period  of  geology.  They  possessed 
teeth,  sunk  in  distinct  sockets,  and  the  limbs  were  extremely 
strong,  and  adapted  for  progression  on  land.  In  some  cases 
the  fore-limbs  were  very  much  smaller  than  the  hind-limbs, 
and  there  is  reason  to  suppose  that  some  of  these  extraordi- 
nary animals,  though  of  enormous  size,  walked  habitually 
upon  their  hind-legs,  like  Birds.  It  is  also  interesting  to  note 
that  the  gigantic  footprints  of  the  Sandstones  of  the  Connecti- 
cut Valley,  formerly  regarded  as  formed  by  Birds,  are  now 
with  great  probability  looked  upon  as  truly  the  tracks  of  Dei- 
nosaurian  Reptiles. 


CHAPTER  XXIX. 

CLASS  IV.— AVES. 

THE  fourth  class  of  the  Vertebrates  is  that  of  the  Birds  or 
Aves,  which  may  be  shortly  defined  as  being  "  oviparous  Ver- 
tebrates, with  warm  blood,  a  double  circulation,  and  a  cover- 
ing of  feathers"  (Owen).  The  other  leading  characters  which 
separate  the  Birds  from  the  other  Vertebrata  are  that  the  red 
blood-corpuscles  are  nucleated,  the  skull  articulates  with  the 
spine  by  a  single  articulating  surface  (or  condyle),  the  breath- 
ing-organs are  in  the  form  of  lungs,  which  communicate  with 
a  variable  number  of  air-sacs  scattered  through  the  body,  and 
the  fore-limbs  are  never  terminated  (in  existing  birds)  by  more 
than  two  fingers,  ending  in  claws,  and  are  generally  modified 
so  as  to  form  "  wings  "  or  organs  of  flight. 

The  feathers,  which  form  such  a  distinctive  character  of 
birds,  are  formed  by  a  modification  of  the  outer  layer  of  the. 
skin  (epidermis),  and  from  their  non-conducting  nature  they 
serve  to  maintain  the  high  temperature  of  the  body  which  is 
so  characteristic  of  the  class.  A  typical  feather,  such  as  one 
of  the  long  feathers  of  the  tail  or  wing,  consists  of  the  follow- 
ing parts :  1.  A  horny  cylindrical  tube,  which  forms  the  lowest 
portion  of  the  feather,  and  is  termed  the  "quill."  2.  The 
"  shaft,"  which  forms  the  central  axis  of  the  feather,  and  which 
is  simply  the  continuation  of  the  "  quill."  The  under  surface 
of  the  shaft  is  always  marked  by  a  strong  longitudinal  groove, 
and  it  consists  of  a  horny  sheath,  filled  with  a  white  spongy 
material,  not  unlike  the  pith  of  a  plant.  3.  The  "  webs,"  which 
form  the  lateral  expansions  of  the  feather,  and  are  attached 
to  the  sides  of  the  shaft.  Each  web  is  composed  of  a  number 
of  small  branches,  called  the  "  barbs,"  and  'each  barb,  in  turn, 
is  furnished  with  a  series  of  smaller  fibres  called  the  "  bar- 
bules."  As  a  rule,  the  barbs  are  all  kept  in  connection  with 
12 


254  VERTEBRATE  ANIMALS. 

one  another  by  means  of  the  barbules,  the  ends  of  which  are 
hooked.  Toward  the  base  of  the  shaft,  however,  the  barbs 
are  usually  more  or  less  separate  and  placed  at  a  distance  from 
one  another,  constituting  what  is  known  as  the  "  down."  In 
the  Ostriches  and  the  birds  allied  to  them,  all  the  barbs  are 
disunited  and  placed  at  a  distance,  and  they  are  often  not  at 
all  unlike  hairs  in  appearance.  The  feathers  of  birds  not  only 
greatly  conduce  to  the  high  temperature  of  the  body,  but  also 
serve  to  keep  out  moisture,  to  which  end  there  is  a  peculiar 
oil-gland  at  the  base  of  the  tail,  with  the  secretion  of  which 
the  bird  anoints  its  plumage. 

The  skeleton  of  birds  exhibits  many  points  of  peculiar 
interest,  mostly  in  adaptation  to  an  aerial  mode  of  life ;  but 
only  some  of  the  more  important  of  these  can  be  noticed  here. 
The  entire  skeleton  is  at  the  same  time  peculiarly  compact 
and  singularly  light,  the  compactness  being  due  to  the  pres- 
ence of  an  unusual  quantity  of  phosphate  of  lime,  and  the 
lightness  to  the  fact  that  many  of  the  bones  are  filled  with  air 
in  place  of  marrow.  The  cervical  region  (neck)  of  the  verte- 
bral column  is  unusually  long  and  flexible,  since  the  fore-limbs 
are  useless  as  organs  of  prehension,  and  all  these  functions 
have  to  be  performed  by  the  beak.  In  all  birds  the  neck  is,  at 
any  rate,  sufficiently  long  to  allow  of  the  application  of  the 
beak  to  the  tail,  so  as  to  permit  of  the  cleaning  and  oiling  of 
the,  whole  plumage.  The  vertebrae  which  form  the  back  or 
dorsal  region  of  the  spine  are  generally  more  or  less  immov- 
ably connected  together,  so  as  to  give  a  base  of  resistance  to 
the  wings.  In  the  Ostrich,  however,  and  in  other  birds  in 
which  the  power  of  flight  is  either  very  limited  or  is  absent, 
the  dorsal  vertebrae  are  more  or  less  movable  one  upon  the 
other.  The  vertebrae  which  follow  the  dorsal  region  of  the 
spine  are  all  amalgamated  together  to  form  a  single  bony 
mass,  which  is  termed  the  "  sacrum,"  and  this,  in  turn,  is 
united  on  both  sides  with  the  bones  which  form  the  pelvic 
arch,  which  carries  the  hind-limbs.  The  vertebrae  of  the  tail 
are  more  or  less  movable  upon  one  another ;  and  in  almost  all 
living  birds,  when  fully  grown,  the  last  joint  of  the  tail  (Fig. 
129,  B,  s)  is  a  long,  slender,  ploughshare-shaped  bone,  which 
is  really  composed  of  several  vertebrae  united  together.  It  is 
usually  set  on  at  an  angle  nearly  perpendicular  to  the  axis  of 
the  body,  and  it  serves  to  support  the  great  tail-feathers, 
which  act  as  a  rudder  during  flight.  It  also  serves  to  support 
the  oil-gland,  which  supplies  the  secretion  with  which  the 
feathers  are  lubricated.  The  skull  in  birds  has  its  several 


AVES.  255 

bones  generally  so  amalgamated  in  the  adult,  that  it  forms  a 
bony  case  of  a  single  piece,  the  lower  jaw  alone  remaining 
movable.  The  head  is  jointed  to  the  spine  by  no  more  than 
a  single  articulating  surface  or  condyle.  The  beak,  which 
forms  such  a  conspicuous  feature  in  birds,  is  composed  of  two 
halves,  an  upper  half  or  "upper  mandible,"  and  a  "lower 
mandible."  The  lower  mandible,  like  the  lower  jaw  of  all  the 
Sauropsida,  is  at  first  composed  of  several  pieces,  but  these 
are  all  undistinguishably  united  in  the  adult,  and  the  two 
halves  of  the  jaw  are  also  amalgamated  together.  In  no  adult 
bird  are  teeth  ever  developed  in  either  mandible;  but  both 
mandibles  are  sheathed  in  horn,  constituting  the  "  beak,"  and 
the  margins  of  this  sheath  are  sometimes  serrated. 

The  most  characteristic  points,  however,  in  the  skeleton  of 
the  birds,  are  to  be  found  in  the  structure  of  the  limbs.  The 
cavity  of  the  chest  or  thorax  is  bounded  behind  by  the  dorsal 
vertebrae,  on  the  sides  by  the  ribs,  and  in  front  by  the  breast- 
bone or  sternum.  The  ribs  vary  in  number  from  seven  to 
eleven  pairs,  and  in  most  birds  each  rib  gives  off  a  peculiar 
process  (Fig.  128,  B),  which  passes  over  the  rib  next  in  suc- 
cession behind.  In  front  the  ribs  are  jointed  to  a  series  of 
straight  bones,  which  are  called  the  "  sternal  ribs,"  and  these, 
in  turn,  are  movably  articulated  to  the  breastbone  in  front. 
According  to  Owen,  these  sternal  ribs  are  "  the  centres  upon 
which  the  respiratory  movements  hinge."  In  front  the  cavity 
of  the  chest  is  completed  by  an  enormously-expanded  breast- 
bone or  sternum  (Fig.  128,  A),  which,  in  most  birds  of  any 
powers  of  flight,  extends  more  or  less  over  the  abdominal 
cavity  as  well.  The  sternum  of  all  birds  which  possess  the 
power  of  flight  is  characterized  by  the  presence  of  a  prominent 
ridge  or  "keel"  (Fig.  128,  A,  J),  to  which  are  attached  the 
great  muscles  (pectoral  muscles)  which  move  the  wings.  As 
a  general  rule,  the  size  of  this  crest  or  keel  gives  a  tolerably 
just  estimate  of  the  flying  powers  of  the  bird  to  which  it  be- 
longed. The  keel  is,  of  course,  most  largely  developed  in 
those  birds  which  possess  the  power  of  flight  in  its  greatest 
perfection ;  and  in  those  which  do  not  fly,  such  as  the  Ostrich, 
there  is  no  sternal  keel  at  all.  The  pectoral  arch  or  shoulder- 
girdle  of  birds  consists  of  the  shoulder-blades  (scapulas),  the 
clavicles  or  collar-bones,  and  of  two  bones,  which  are  distinct 
in  birds,  and  are  called  the  "  coracoid  bones."  The  shoulder- 
blades  (s  s)  are  usually  long  and  narrow  bones.  The  coracoid 
bones  (IcJc)  correspond  with  the  part  of  the  shoulder-blade 
which  is  known  in  most  of  the  Mammals  as  the  "coracoid 


256 


VERTEBKATE  ANIMALS. 


FIG.  128. — A,  Breastbone,  shoulder-girdle,  and  fore-limb  of  Penguin  (after  Owen);  &  Breast- 
bone (sternum),  with  its  prominent  ridge  or  keel ;  s $  Shoulder-blades  (seapulce)  ;  k  k 
Coracoid  bones ;  o  Furculum  or  Merry -thought,  composed  of  the  united  collar-bones 
(clavicles) ;  h  Bone  of  the  upper  arm  or  humerus  ;  r  Kadius ;  u  Ulna,  forming  together 
the  forearm;  q  Bones  of  the  wrist  or  carpus;  t  Thumb;  m  Metacarpus;  p  Phalanges 
of  the  fingers.  B,  Kibs  of  the  Golden  Eagle ;  a  a  Bibs  giving  off  processes  (b  V) ;  c  c 
Sternal  ribs. 


process ; "  and  in  birds  they  are  not  only  separate  bones,  but 
they  are  the  strongest  bones  of  the  pectoral  arch.  They  are 
more  or  less  nearly  vertical,  and  they  form  fixed  points  for 
the  downward  stroke  of  the  wing.  The  collar-bones  or  clavi- 
cles (c)  in  the  great  majority  of  birds  are  united  together  in 
front,  so  as  to  form  a  somewhat  V-shaped  bone,  which  is  tech- 
nically called  the  "furculum,"  but  is  familiarly  called  the 
"  merry-thought."  The  function  of  this  clavicular  arch  is  to 
keep  the  wings  asunder  during  their  downward  stroke,  and 
the  strength  of  the  furculum  varies,  therefore,  with  the  powers 
of  flight  enjoyed  by  each  bird.  The  bones  which  form  the 
limb  proper,  or  "  wing,"  are  considerably  modified  to  suit  the 
special  function  of  flight,  but  essentially  the  same  parts  are 
present  as  in  the  fore-limb  of  the  Mammals.  The  upper  arm 
is  constituted  by  a  single  bone,  the  humerus  (h\  which  is  gen- 
erally short  and  stout,  The  forearm  is  composed  of  two 
bones,  the  radius  (r)  and  the  ulna  (u),  of  which  the  ulna  is 
the  bigger.  These  are  followed  by  the  small  bones,  which 


AVES. 


257 


form  the  wrist  or  carpus  (<?),  but  these  are  reduced  to  two  in 
number.  The  carpus  is  followed  by  the  bones  which  con- 
stitute the  root  of  the  hand  or  metacarpus  (m),  but  these  are 
also  reduced  to  two,  instead  of  being  five  in  number,  as  they 
are  in  most  Mammals.  The  two  metacarpal  bones  are  also 
amalgamated  together  at  both  ends,  so  as  to  form  a  single 
piece,  at  the  base  of  which,  on  its  outer  side,  is  a  rudimentary 
digit,  the  "thumb"  (£),  which  carries  a  tuft  of  feathers, known 
as  the  "  bastard  wing."  The  metacarpal  bones,  finally,  sup- 
port each  a  single  finger  (p),  of  which  one  is  never  composed 
of  more  than  one  bone  or  phalanx,  while  the  other  is  com- 
posed of  two  or  three  phalanges.  (To  understand  thoroughly 
the  leading  modifications  of  the  limbs  of  birds,  the  student 
will  do  well  to  refer  to  the  general  description  of  the  limbs  of 
Vertebrates,  p.  200,  Figs.  96,  97.) 

As  regards  the  composition  of  the  hind-limb  in  birds,  the 
two  halves  of  the  pelvic  arch  (i.  e.,  the  innominate  bones)  al- 


FIG.  129. — A,  Pelvis  and  bones  of  the  Leg  of  the  Loon  or  Diver  (after  Owen) :  i  Innominate 
bone ;  /  Thigh-bone  (femwr) ;  t  Tibia,  r  fibula,  together  forming  the  shank ;  m  Tarso- 
metatarsus ;  p  Phalanges  of  the  toes.  B,  Tail  of  the  Golden  Eagle ;  a  Ploughshare- 
shaped  bone,  carrying  the  great  tail-feathers. 


258  VERTEBRATE  ANIMALS. 

ways  form  a  single  piece  each,  and  they  are  always  firmly 
united  with  the  sacral  region  of  the  spine.  With  the  single 
exception,  however,  of  the  Ostrich,  they  do  not  unite  below, 
but  remain  separate.  As  in  the  higher  Vertebrates,  the  lower 
limb  consists  of  a  thigh-bone  (femur),  a  shank,  composed  of 
two  bones  (tibia  and  Jld&ftz),  a  tarsus,  a  metatarsus,  and  pha- 
langes, but  some  of  these  parts  are  obscured  by  coalescence. 
The  thigh-bone  or  femur  (Fig.  129,  /)  is  generally  very  short, 
comparatively  speaking ;  and  the  chief  bcne  of  the  leg  is  the 
tibia  (£),  to  which  a  thin  and  tapering  fibula  (r)  is  attached. 
In  the  regular  typical  limb  of  a  Vertebrate  animal  the  tibia 
and  fibula  would  be  followed  by  a  series  of  small  bones,  called 
the  tarsus,  constituting  the  ankle-joint  (Fig.  97) ;  and  the  tar- 
sus would  in  turn  be  followed  by  a  series  of  bones  constituting 
the  root  of  the  foot,  or  metatarsus.  In  Birds,  however,  the 
tibia  and  fibula  are  followed  by  a  single  cylindrical  bone, 
which  is  called  the  "  tarsc-metatarsus"  (m)9  and  which  is 
formed  by  the  amalgamation  of  the  entire  metatarsus  with  the 
whole  or  a  portion  of  the  tarsus.  The  most  probable  view  is 
that  only  the  lower  portion  of  the  tarsus  is  present  in  the 
tarso-metatarsus,  and  that  the  upper  portion  of  the  tarsus  is 
fused  with  the  lower  end  of  the  tibia.  In  this  case  the  ankle- 
joint  is  placed  in  the  middle  of  the  tarsus.  The  tarso-meta- 
tarsus is  followed  below  by  the  foot,  which  consists  in  most 
birds  of  four  toes,  of  which  three  are  directed  forward  and 
one  backward.  In  no  wild  birds  are  there  more  than  four 
toes;  but  some  domesticated  varieties  possess  a  fifth.  In 
most  birds  with  four  toes,  the  toe  which  is  directed  backward 
consists  of  two  phalanges;  the  innermost  of  the  three  forwaid 
toes  has  three  phalanges,  the  next  has  four,  and  the  outer- 
most toe  is  composed  of  five.  In  many  birds,  such  as  the 
Parrots,  the  outermost  toe  is  turned  backward,  so  that  there 
are  two  toes  in  front  and  two  behind.  In  the  Swifts,  again, 
all  the  four  toes  are  turned  forward.  In  many  of  the  swim- 
ming-birds (Natatores)  the  hinder  toe  is  wanting  or  rudimen- 
tary ;  and  in  the  Ostrich  both  this  and  the  next  toe  are  ab- 
sent, so  that  the  foot  consists  of  no  more  than  two  toes. 

The  digestive  system  in  Birds  consists  of  the  beak,  tongue, 
gullet,  stomach,  intestine,  and  cloaca,  with  certain  accessory 
glands.  There  are  no  teeth,  and  the  beak  is  employed,  in  dif- 
ferent birds,  for  holding  and  tearing  the  prey,  for  prehension, 
for  climbing,  and  in  some  cases  as  an  organ  of  touch,  being  in 
these  last  instances  more  or  less  soft,  and  supplied  with 
nervous  filaments.  In  many  birds,  too,  the  base  of  the  bill  is 


AVES.  259 

surrounded  by  a  circle  of  naked  skin,  constituting  what  is 
called  the  "  cere,"  and  this,  too,  serves  as  an  organ  of  touch. 
The  tongue  of  birds  can  rarely  be  looked  upon  as  an  organ  of 
taste,  since  it  is  generally  cased  in  horn,  like  the  mandibles. 
It  is  principally  employed  as  an  organ  of  prehension,  but  it  is 
soft  and  fleshy  in  the  Parrots,  and  in  them,  doubtless,  acts  as 
an  organ  of  taste.  Salivary  glands  are  always  present,  but 
they  are  rarely  of  large  size,  and  are  often  of  extremely  simple 
structure.  In  accordance  with  the  length  of  the  neck,  the 
gullet  is  usually  very  long  in  birds,  and  is  generally  very  di- 
latable. In  the  flesh-eating  and  grain-eating  birds  the  gullet 
is  dilated  (Fig.  130,  c)  into  a  pouch  which  is  called  the 


FIG.  130.— Digestive  System  of  the  common  Fowl  (after  Owen),  o  Gullet ;  c  Crop ;  p  Pro- 
ven triculus,  Q  Gizzard;  sm  Small  intestine;  k  Intestinal  caeca:  I  Large  intestine; 
cl  Cloaca. 

"  crop,"  and  is  situated  in  the  lower  part  of  the  neck,  just  in 
front  of  the  merry-thought.  This  may  be  simply  a  dilatation 
of  the  tube  of  the  gullet,  or  it  may  be  a  single  or  double 
pouch.  The  function  of  the  crop  is  to  detain  the  food,  for  a 
longer  or  shorter  period,  according  to  its  nature,  before  it  is 
submitted  to  the  action  of  the  proper  digestive  organs.  In  the 
Pigeons,  the  food  which  has  been  previously  softened  in  the 


260  VERTEBRATE  ANIMALS. 

crop  is  returned  to  the  mouth,  and  supplied  to  the  young  in  a 
state  suitable  for  digestion.  The  gullet,  after  leaving  the 
crop,  shortly  opens  into  a  second  cavity,  called  the  "  proven- 
triculus,"  which  is  the  true  digesting  stomach,  and  is  richly 
supplied  with  glands  which  secrete  the  digestive  fluid  or  gas- 
tric juice  (p).  This,  in  turn,  opens  into  a  muscular  cavity 
which  is  called  the  "gizzard"  (#),  and  which  leads  into  the 
commencement  of  the  small  intestine.  The  characters  of  the 
gizzard  vary  with  the  nature  of  the  food.  In  the  birds  of 
prey,  which  live  on  a  easily-digested  animal  diet,  the  walls  of 
the  gizzard  are  thin  and  membranous.  In  the  grain-eating 
birds,  such  as  the  fowls,  whose  hard  food  requires  to  be 
crushed  before  it  can  be  properly  digested,  the  walls  of  the 
gizzard  are  extremely  thick  and  muscular,  and  the  inner  lin- 
ing is  hard  and  horny.  In  these  birds  the  gizzard  constitutes 
a  kind  of  grinding  apparatus,  like  the  stones  of  a  mill ;  while 
the  "crop"  may  be  compared  to  the  "hopper"  of  the  mill, 
since  it  supplies  to  the  gizzard  "  small  successive  quantities 
of  food  as  it  is  wanted  (Owen).  The  grinding  action  of  the 
gizzard  is  further  assisted  by  the  small  pebbles  and  gravel 
which,  as  is  well  known,  so  many  birds  are  in  the  habit  of 
swallowing.  These  pebbles  take  the  place  of  teeth,  and  there 
can  be  no  doubt  that  they  are  in  many  cases  essential  to 
health,  the  bird  being  otherwise  unable  to  triturate  its  food 
properly.  The  intestinal  canal  extends  from  the  gizzard  to 
the  cloaca  (cZ),  and  is  comparatively  short.  The  secretions  of 
the  liver  and  pancreas  are  poured  into  the  commencement  of 
the  small  intestine.  The  commencement  of  the  large  intestine 
is  furnished  in  most  birds  with  two  blind  tubes  or  caeca  (k). 
These  vary  considerably  in  length  in  different  birds,  and  are 
sometimes  wanting;  while  their  exact  function  is  still  ques- 
tionable. The  large  intestine  is  seldom  more  than  a  tenth 
part  of  the  length  of  the  body,  and  is  generally  conducted 
straight  from  the  caeca  to  the  cloaca.  The  cloaca  is  a  com- 
mon cavity  which  in  birds,  as  in  Reptiles,  receives  the  termi- 
nation of  the  intestine  and  the  ducts  of  the  generative  and 
urinary  organs  (ct). 

Respiration  is  effected  in  Birds  more  completely,  exten- 
sively, and  actively,  than  in  any  other  class  of  the  Vertebrata, 
and,  as  the  result  of  this,  their  average  temperature  is  higher 
than  in  any  other  Vertebrates.  This  extensive  development 
of  the  respiratory  process  is  due  to  the  fact  that  air  is  admit- 
ted in  Birds  not  only  to  the  lungs,  but  also  to  the  interior  of 
a  greater  or  less  number  of  the  bones,  and  to  a  series  of  air- 


AYES.  261 

receptacles  which  are  scattered  through  various  parts  of  the 
body.  The  lungs  are  two  in  number,  of  a  bright-red  color, 
and  spongy  texture,  and  they  are  confined  to  the  back  part 
of  the  chest.  They  differ  from  the  lungs  of  Mammals  in  not 
being  freely  suspended  in  a  membranous  bag  (pleura),  but  in 
being  fixed  to  the  back  wall  of  the  chest.  The  thoracic  and 
abdominal  cavities  are  not  separated  from  one  another  by  a 
complete  partition  (midriff  or  diaphragm)  as  the  Mammals,  but 
the  common  thoracico-abdominal  cavity  is  subdivided  by  means 
of  membranous  partitions  into  a  series  of  cavities  or  sacs,  which 
are  termed  the  "air-receptacles."  These  air-sacs  are  filled 
with  air  from  the  lungs,  and  vary  considerably  in  number  and 
size  in  different  birds.  They  not  only  serve  greatly  to  reduce 
the  specific  gravity  of  the  body,  but  also  assist  largely  in  the 
aeration  of  the  blood.  Connected  with  the  air-receptacles, 
and  supplementing  their  action  in  both  of  these  respects,  is  a 
series  of  cavities  occupying  the  interior  of  a  greater  or  less 
number  of  the  bones,  and  also  containing  air.  In  young  birds 
these  air-cavities  in  the  bones  do  not  exist,  and  the  bones  are 
simply  filled  with  marrow,  as  in  the  Mammals.  In  the  Pen- 
guin, which  does  not  fly,  none  of  the  bones  contain  air-cavities 
or  are  "  pneumatic ; "  and  in  the  Ostrich  only  a  few  of  the 
bones  contain  air.  In  the  Pelican  and  Gannet  all  the  bones 
of  the  skeleton,  except  the  phalanges  of  the  toes,  are  per- 
meated by  air;  and  in  the  Hornbill  even  these  are  pneu- 
matic. 

The  heart  in  all  birds  consists  of  four  chambers,  and  the 
two  sides  of  the  heart  are  completely  separated  from  one 
another.  In  all  essential  details,  as  regards  the  structure  of 
the  heart  and  great  vessels,  and  the  course  of  the  circulating 
fluid,  Birds  agree  with  Mammals.  The  impure  venous  blood 
which  has  traversed  the  body  is  returned  by  the  great  veins 
to  the  right  auricle.  From  the  right  auricle  it  passes  into  the 
right  ventricle,  from  which  it  is  driven  by  the  pulmonary  artery 
to  the  lungs.  Having  been  submitted  to  the  action  of  the  air 
contained  in  the  lungs,  and  having  been  thereby  changed  into 
arterial  blood,  the  blood  is  sent  back  to  the  left  auricle  by 
means  of  the  pulmonary  veins.  Thence  it  passes  into  the 
left  ventricle,  by  which  it  is  again  propelled  throughout  the 
whole  body,  to  return  again  as  venous  blood  to  the  right  side 
of  the  heart.  The  heart,  therefore,  of  birds,  differs  from  that 
of  reptiles  in  consisting  of  two  sides,  each  composed  of  an 
auricle  and  ventricle,  the  right  side  being  wholly  concerned 
with  sending  the  venous  blood  to  the  lungs,  and  the  left  side 


262  VERTEBRATE  ANIMALS. 

being  entirely  occupied  with  sending  the  arterial  blood  to  the 
body.  The  right  side  of  the  heart  is  therefore  venous,  the  left 
side  arterial.  In  all  Reptiles,  on  the  other  hand,  the  two  cir- 
culations— namely,  that  through  the  lungs  and  that  through 
the  body — communicate  with  one  another,  either  in  the  heart 
itself  or  in  its  immediate  neighborhood ;  so  that  both  the  lungs 
and  the  body  are  supplied  with  a  mixture  of  venous  with  arte- 
rial blood.  Though  the  heart  of  Birds  resembles  that  of  Mam- 
mals in  general  structure,  its  cavities  are  "  relatively  stronger, 
their  valvular  mechanism  is  more  perfect,  and  the  contractions 
of  this  organ  are  more  forcible  and  frequent  in  Birds,  in  ac- 
cordance with  their  more  extended  respiration  and  their  more 
energetic  muscular  actions"  (Owen).  The  urinary  organs  of 
birds  consists  of  two  elongated  kidneys,  which  open  by  means 
of  their  ducts  (the  ureters)  into  the  cloaca,  along  with  the  ter- 
mination of  the  intestine  and  the  ducts  of  the  reproductive 
organs.  As  a  general  rule,  the  female  bird  is  provided  with 
only  a  single  ovary — that  of  the  left  side — and  all  birds,  with- 
out exception,  are  oviparous.  The  egg  is  always  enclosed  in 
a  calcareous  shell,  and  is  developed  after  expulsion  from  the 
body,  by  the  process  of  "  incubation  "  or  "  brooding  " — a  pro- 
cess for  which  birds  are  especially  adapted,  in  consequence  of 
their  very  high  average  temperature.  The  young  bird,  when 
ready  for  an  independent  existence,  perforates  the  shell,  often 
by  means  of  a  temporary  calcareous  excrescence  developed 
upon  the  point  of  the  upper  mandible  of  the  bill.  In  some 
birds,  mostly  in  the  case  of  those  which  live  upon  the  ground, 
the  young  are  able  to  run  about  and  look  for  food  directly 
after  they  come  out  of  the  egg,  as  is  seen  in  the  common 
Fowl.  In  most  birds,  however,  the  young  are  liberated  from 
the  egg  in  a  perfectly  helpless  and  naked  condition,  and  re- 
quire to  be  fed  by  their  parents  for  a  longer  or  shorter  time, 
before  they  are  able  to  take  care  of  themselves.  Most  of  these 
birds,  such  as  our  common  song-birds,  reside  in  trees,  and 
build  more  or  less  elaborate  nests. 

As  regards  their  nervous  system,  the  brain  of  Birds  is  rela- 
tively larger  than  the  brain  of  Reptiles,  but  it  is  destitute  of 
those  folds  or  convolutions  which  form  so  marked  a  feature  in 
the  brain  of  most  Mammals.  The  organs  of  sense,  with  the 
exception  of  touch  and  taste,  are  well  developed  in  Birds, 
vision  especially  being  generally  extremely  acute.  The  eyes 
are  always  well  developed,  and  in  no  bird  are  they  ever  want- 
ing or  rudimentary.  The  chief  peculiarity  of  the  eye  of  Birds 
is,  that  its  anterior  portion  (cornea)  forms  the  segment  of  a 


AVES.  263 

much  smaller  circle  than  does  the  eyeball  proper ;  so  that  the 
whole  eye  assumes  a  conical  shape.  Another  peculiarity  is 
that  the  form  of  the  eye  is  maintained  by  means  of  a  circle  of 
from  thirteen  to  twenty  bony  plates,  which  are  placed  in  the 
front  portion  of  the  fibrous  coat  of  the  eye  (sclerotic).  Eye- 
lashes are  almost  universally  absent ;  but,  in  addition  to  the 
ordinary  upper  and  lower  eyelids,  Birds  possess  a  third  mem- 
branous eyelid — the  membrana  nictitans — which  is  placed  on 
the  inner  side  of  the  eye.  This  nictitating  membrane  is  some- 
times transparent,  sometimes  pearly  white,  and  it  can  be  drawn 
over  the  front  of  the  eye  like  a  curtain,  moderating  the  too 
great  intensity  of  the  light.  As  regards  the  organ  of  hearing, 
the  chief  point  to  remark  is  that  Birds  have  mostly  no  external 
ear,  by  means  of  which  the  undulations  of  sound  can  be  col- 
lected and  transmitted  to  the  internal  ear.  In  some  birds, 
however,  as  the  Ostrich,  the  external  opening  af  the  organ 
of  hearing  is  provided  with  a  circle  of  feathers,  which  can  be 
raised  and  depressed  at  will.  In  the  nocturnal  Birds,  also, 
(such  as  Owls),  the  external  opening  of  the  ear  is  protected 
by  a  musculo-membranous  valve,  foreshadowing  the  gristly 
external  ear  of  Mammals.  The  sense  of  smell  is  apparently 
seldom  very  acute  in  Birds,  and  even  the  Birds  of  Prey  appear 
to  seek  their  food  mainly  by  the  sight.  The  external  nostrils 
are  usually  placed  on  the  sides  of  the  upper  mandible,  near  its 
base,  and  form  simple  perforations  which  sometimes  communi- 
cate from  side  to  side.  In  the  curious  Apteryx  of  New  Zea- 
land, the  nostrils  are  placed  at  the  extreme  end  of  the  elon- 
gated beak.  Sometimes  the  nostrils  are  defended  by  bristles, 
and  sometimes  by  a  cartilaginous  scale. 

Before  passing  on  to  a  consideration  of  the  divisions  of 
Birds,  a  few  words  may  be  said  on  the  migrations  of  Birds. 
In  temperate  and  cold  climates,  few  birds  remain  constantly  in 
the  same  region  in  which  they  were  originally  hatched.  Those 
which  do  so  are  called  "  permanent  birds."  Other  birds,  such 
as  the  Woodpeckers,  migrate  from  place  to  place  without  fol- 
lowing any  very  definite  course.  These  are  called  "  wander- 
ing birds,"  and  their  movements  are  chiefly  conditioned  by  the 
scarcity  or  abundance  of  food  in  any  particular  locality.  Other 
birds,  however,  at  certain  seasons  of  the  year,  undertake  long 
journeys,  usually  uniting  for  this  purpose  into  larger  or  smaller 
flocks.  Such  birds — of  which  the  Swallows  are  a  familiar  in- 
stance— are  properly  called  "  migratory  birds,"  and  their  move- 
ments are  conditioned  by  the  necessity  of  having  a  certain 
average  temperature,  without  which  they  cannot  live.  Thus 


264  VERTEBRATE  ANIMALS. 

the  migratory  birds  of  cold  climates,  when  the  cold  season 
comes  on,  travel  to  warmer  countries  ;  but  when  the  hot  sea- 
son of  these  regions  approaches,  they  migrate  back  again  to 
temperate  zones. 


CHAPTER    XXX. 
DIVISIONS  OF  BIRDS. 

BIRDS  may  be  variously  divided,  but  for  our  present  pur- 
pose it  is  most  convenient  to  regard  them  as  divided  into  the 
following-  eight  orders : 

I.  JVatatores  or  Swimming  Birds,  characterized  by  having 
the  feet  webbed,  and  the  legs  short  and  placed  far  back,  while 
the  body  is  closely  covered  with  feathers  and  with  a  thick 
coating  of  down  next  the  skin.    (Me.  Ducks,  Geese,  Pelicans.) 

II.  G-rattatores  or  Wading  Birds,  characterized  by  having 
very  long  legs,  which  are  destitute  of  feathers  from  the  lower 
end  of  the  tibia  downward.     The  toes  are  usually  long  and 
straight,  and  are  never  connected  to  one  another  by  membrane. 
(Ex.  Curlews,  Snipes,  Herons,  Storks.) 

III.  Cursores  or  Running  Birds,  characterized  by  having 
very  short  wings,  which  are  not  used  in  flight ;  the  breast- 
bone is  without  a  ridge  or  keel ;  the  legs  are  very  robust ;  and 
the  hind-toe  is  wanting  or  rudimentary.     (Ex.  Ostriches  and 
Emeus.) 

IV.  Rasores  or  Scratching  Birds,  characterized  by  usually 
having  strong  feet,  with  powerful  blunt  claws,  used  for  scratch- 
ing.    The  upper  mandible  of  the  bill  is  strongly  curved  and 
vaulted,  and  the   nostrils  are  pierced  in  a  membranous  space 
at  its  base,  and  are  covered  by  a  cartilaginous  scale.     (Ex. 
Fowls,  Pheasants,  Pigeons.) 

V.  Scansores  or  Climbing  Birds,  characterized  by  having 
a  climbing  foot,  in  which  two  toes  are  turned  backward  and 
two  forward.     (Ex.  Woodpeckers,  Parrots,  Cuckoos.) 

VI.  Tnsessores  or  Perching  Birds,  characterized  by  having 
short  and  slender  legs,  with  three  toes  in  front  and  one  be- 
hind, the  whole  foot  being  adapted  for  perching.    (Ex.  Larks, 
Linnets,  Swallows,  Crows,  Humming-birds.) 


266 


VERTEBRATE  ANIMALS. 


VII.  Haptores  or  Birds  of  Prey^  characterized  by  having 
a  strong,  sharp-edged,  and   sharp-pointed  beak,  adapted  for 
tearing  animal  food,  and  by  their  robust  legs,  armed  with  four 
toes,  three  in  front  and  one  behind,  all  of  which  are  furnished 
with  long,  strong,   crooked  claws  or  talons.      (Ex.   Eagles, 
Hawks,  Owls.) 

VIII.  Saururce  or  Lizard-tailed  Birds,  characterized  by 
having  a  tail  longer  than  the  body,  composed  of  numerous 
distinct  and  movable  vertebrae,  each  of  which  carries  a  single 
pair  of  quill-feathers.     (This  order  includes  only  the  remark- 
able  fossil  bird,  the  Archceopteryx.) 

OEDEE  I.  NATATOEES  (Lat.  natator,  a  swimmer). — The 
order  of  the  Swimming  Birds  comprises  birds  which  are  as 
much  at  home  in  the  water  as  upon  land,  or  even  more  so.  In 
accordance  with  their  aquatic  mode  of  life,  the  JVatatores  have 
a  boat-shaped  body,  generally  elongated,  and  usually  having  a 
long  neck.  The  legs  are  short,  and  are  placed  behind  the  cen- 


FIG.  131.— Natatores.    Penguin  (SpJiemiscw  demersm\ 


DIVISIONS  OF  BIRDS.  267 

tre  of  gravity  of  the  body ;  this  position  enabling  them  to  act 
admirably  as  swimming-paddles,  at  the  same  time  that  it  ren- 
ders the  gait  upon  dry  land  comparatively  awkward  and  shuf- 
fling. The  toes  in  all  the  Natatores  are  webbed  to  a  greater 
or  less  extent,  or,  in  other  words,  are  united  by  a  membrane 
(Fig.  131).  In  many  the  web  or  membrane  between  the  toes 
is  stretched  completely  from  toe  to  toe,  but  in  others  the  mem- 
brane is  divided  between  the  toes,  so  that  the  feet  are  only 
imperfectly  webbed.  As  their  aquatic  mode  of  life  exposes 
them  to  great  reductions  of  temperature,  the  body  in  the  Na- 
tatorial birds  is  closely  covered  with  feathers,  with  a  thick 
covering  of  down  next  the  skin.  They  are  further  protected 
against  becoming  wet  while  in  the  water  by  the  great  develop- 
ment of  the  oil-gland  at  the  tail,  by  means  of  which  the  dense 
plumage  is  kept  constantly  oiled.  As  a  rule,  the  Natatorial 
birds  are  polygamous,  each  male  having  several  females ;  and 
the  young  are  hatched  in  a  condition  not  requiring  assistance 
from  their  parents,  being  able  to  swim  about  and  procure  food 
for  themselves  the  instant  they  are  liberated  from  the  egg. 

Among  the  more  important  families  of  the  Natatores  may 
be  enumerated  the  Penguins  (Spheniscidce) ,  the  Auks  (Al- 
cidce),  the  Gulls  and  Terns  (Laridce),  the  Petrels  (Procella- 
ridoe},  the  Pelicans  (Pelicanus),  the  Cormorants  (Phalacro- 
corax),  the  Gannets  (Sula),  the  Ducks  (Anatidce),  the  Geese 
(AnserincB\  and  the  Swans  ( CygnidcB). 

The  Penguins  and  Auks,  with  their  allies  the  Divers,  Guil- 
lemots, and  Grebes,  have  rudimentary,  or  at  any  rate  small, 
wings,  and  are  all  more  at  home  in  the  water  than  upon  land. 
The  Gulls,  Terns,  and  Petrels,  on  the  contrary,  are  all  birds  of 
powerful  flight,  and  some  of  them,  such  as  the  Albatross,  are 
habitually  found  hundreds  of  miles  from  the  nearest  land. 
The  Pelicans,  with  their  allies  the  Cormorants,  Frigate-birds, 
and  Darters,  are  excellent  flyers,  and  aleo  not  uncommonly 
perch  on  trees,  which  few  Natatorial  birds  do.  They  are  dis- 
tinguished by  having  the  hinder  toe  directed  inward,  and 
united  to  the  innermost  of  the  front  toes  by  a  continuous 
membrane.  The  Gannets,  Ducks,  Geese,  and  Swans,  have  the 
bill  very  much  flattened  and  covered  by  a  soft  skin.  The 
edges  of  the  bill  are  also  furnished  with  a  series  of  transverse 
plates,  which  form  a  kind  of  fringe  or  "  strainer,"  by  means 
of  which  these  birds  sift  the  mud  in  which  they  habitually 
seek  their  food. 

OEDEB  II.  GKALLATOEES  (Lat.  grattce,  stilts). — The  Wading 
Birds  for  the  most  part  frequent  moist  situations,  such  as 


268 


VERTEBRATE  ANIMALS. 


marshes  and  shallow  ponds,  the  shore  of  the  sea,  or  the  banks 
of  rivers  or  lakes,  though  some  of  them  keep  entirely,  or  al- 
most entirely,  to  the  dry  land,  In  accordance  with  their  semi- 
aquatic,  amphibious  habits,  the  Waders  are  distinguished  by 
the  great  length  of  their  legs — the  increase  in  length  being 
chiefly  due  to  the  elongation  of  the  tarso-metatarsus.  The 
legs  (Fig.  132)  are  also  unfeathered  or  naked,  as  far  as  the 


FIG.  132.— Grallatores.    Common  Heron  (Ardea  cinerea). 

lower  end  of  the  tibia,  at  any  rate.  There  are  three  anterior 
toes,  and  usually  a  short  hind-toe ;  but  the  toes  are  never  com- 
pletely webbed,  though  they  are  sometimes  partially  palmate. 
The  wings  are  long,  and  the  power  of  flight  is  usually  consid- 
erable ;  but  the  tail  is  very  short,  and  its  function  as  a  rudder 
is  chiefly  transferred  to  the  long  legs,  which  are  stretched  out 
behind  in  flight.  The  beak  is  almost  always  of  great  length, 
generally  longer  than  the  head  (Fig.  132),  and  usually  more  or 
less  pointed,  though  it  is  sometimes  flattened.  In  the  Avocet 
the  bill  is  curved  upward,  instead  of  being  straight,  or  bent 
downward,  as  is  generally  the  case.  The  typical  Waders,  as 
before  said,  spend  most  of  their  time  wading  about  in  shallow 


DIVISIONS  OF  BIRDS.  269 

water,  feeding  upon  small  fishes,  shell-fish,  worms,  and  insects. 
Others,  such  as  the  Storks,  live  mostly  upon  the  land,  and  are 
more  or  less  exclusively  vegetable-feeders. 

Among  the  more  important  Grallatorial  birds  are  the  Rails 
(Rattidce),  Water-hens  (Gallinulce), Cranes  (Gruidce),  Herons 
(Ardeidce],  Storks  (Ciconince),  Snipes  (Scolopacidce),  Sand- 
pipers (Tringidce),  Curlews  (Numenius),  Plovers  (Charadrii- 
dve),  and  Bustards  (Otidce). 

The  Rails  are  more  or  less  terrestrial  in  their  habits,  but 
inhabit  marshes  and  fens.  Good  examples  are  the  Marsh 
Hen  (JRallus  elegans)  and  the  Virginia  Rail  (R.  Virginianus) 
of  North  America,  and  the  Corn  Crake  ( Crex  pratensis)  of 
Europe.  The  Water-hens  ( Gallinula)  and  Coots  (Fulica)  are 
aquatic  or  semi-aquatic,  swimming  and  diving  with  the  great- 
est ease.  The  Cranes  are  in  the  main  vegetable-feeders,  and 
inhabit  dry  plains.  The  Herons,  Egrets,  Bitterns,  and  Night 
Herons,  form  a  beautiful  family  of  wading  birds,  represented 
in  almost  every  portion  of  the  known  world.  Nearly  allied  to 
these  are  the  brilliantly-colored  Ibises  (Tantalince),  which 
inhabit  all  warm  countries.  The  Ciconince  are  all  large  birds, 
and  comprise  the  Storks  and  Adjutant,  while  the  Spoon- 
bills are  mainly  separated  from  them  by  their  flattened,  spoon- 
shaped  bill.  The  Scolopacidce,  comprising  the  Snipes  and 
Woodcocks,  the  Tringidce  (or  Sandpipers),  the  Curlews  (Nu- 
menius),  and  various  other  allied  birds,  are  distinguished  from 
the  preceding  by  the  possession  of  a  long,  soft,  slender  bill, 
which  is  used  in  probing  the  ground  for  food.  In  the  Chara- 
driidce  are  comprised  the  Oyster-catchers,  Turnstones,  Lap- 
wings, Plovers,  Thick-knee,  and  many  other  familiar  birds. 
Lastly,  the  Otidce  comprise  only  the  Bustards,  which  are  ex- 
clusively confined  to  the  Old  World,  and  make  a  decided  ap- 
proach to  the  Cursorial  Birds. 

OKDEK  III.  CUBSOBES  (Lat.  curro,  I  run). — The  Running 
or  Cursorial  Birds,  comprising  the  Ostrich,  Cassowary,  Emeu, 
Rhea,  and  Apteryx,  are  characterized  by  the  rudimentary  con- 
dition of  the  wings,  which  are  useless  as  organs  of  flight,  and 
by  the  compensating  length  and  strength  of  the  legs.  In  ac- 
cordance with  this  condition  of  the  limbs,  the  bones  have  few 
air-cells,  and  the  breast-bone  is  destitute  of  the  prominent 
ridge  or  keel  to  which  the  great  muscles  of  the  wings  are  at- 
tached. The  two  sides  of  the  pelvis  are  united  together  below 
in  the  Ostrich,  and  in  all  the  pelvic  arch  has  great  strength 
and  stability.  The  legs  are  extremely  powerful,  and  the  hinder 


270  VERTEBRATE  ANIMALS. 

toe  is  wanting  in  all  except  the  Apteryx,  in  which  it  is  present 
in  a  rudimentary  condition.  The  front  toes  (Fig.  133)  are 
either  two  or  three  in  number,  and  are  furnished  with  strong 
blunt  claws  or  nails.  The  feathers  present  the  remarkable 
peculiarity,  that  the  barbs,  instead  of  being  connected  by 
means  of  the  barbules,  are  disconnected  and  separate  from 
one  another,  thus  coming  to  resemble  hairs  in  appearance. 


FIG.  133.— Cursores.     The  Apteryx  AmtraUs  (Gould). 

The  African  Ostrich  (Struthio  camelus),  which  is  one  of 
the  best-known  members  of  this  order,  inhabits  the  desert 
plains  of  Africa  and  Arabia,  and  is  the  largest  of  living  birds, 
attaining  a  height  of  from  six  to  eight  feet.  The  head  and 
neck  are  nearly  naked,  and  the  quill-feathers  of  the  wings  and 
tail  have  their  barbs  wholly  separate,  constituting  the  ostrich- 
plumes  of  commerce.  The  legs  are  extremely  strong,  and  the 
feet  have  only  two  toes  each.  The  Ostriches  run  with  extraor- 
dinary speed,  and  can  outstrip  the  fastest  horse.  They  are 
polygamous,  each  male  having  several  females,  and  they  keep 
together  in  larger  or  smaller  flocks.  The  American  Ostriches 
or  Rheas  are  much  smaller  than  the  African  Ostrich,  and  have 
the  head  feathered,  while  the  feet  are  furnished  with  three 
toes  each.  They  inhabit  the  great  plains  of  South  America, 
and  are  polygamous.  The  Emeu  (Dromaius)  is  exclusively 
confined  to  New  Holland.  In  size  it  nearly  equals  the  African 


DIVISIONS   OF  BIRDS.  271 

Ostrich,  standing  from  five  to  seven  feet  in  height,  and  it  is 
not  uncommonly  kept  as  a  domestic  pet.  The  Cassowary 
( Gasuarius  galeatus)  inhabits  the  Moluccan  Islands  and  New 
Guinea,  and  was  first  brought  alive  to  Europe  by  the  Dutch. 
It  stands  about  five  feet  in  height,  and  possesses  a  singular 
horny  crest  upon  the  head.  Another  species  of  Cassowary  in- 
habits Australia,  and  other  species  are  known  to  exist  in  the 
Indian  Archipelago.  The  last  of  the  living  Cursorial  birds  is 
the  curious  bird,  the  Apteryx  (Fig.  133)  of  New  Zealand.  In 
this  remarkable  bird  the  beak  is  extremely  long  and  slender, 
and  the  nostrils  are  placed  at  the  extremity  of  the  upper  man- 
dible. The  legs  are  comparatively  short,  and  there  is  a  rudi- 
mentary hind-toe,  provided  with  a  claw.  The  feathers  of  the 
general  plumage  are  long  and  hair-like,  and  the  wings  are 
altogether  rudimentary. 

ORDER  IV.  RASOBES  (Lat.  rado,  I  scratch). — The  Scratch- 
ing Birds — or,  as  they  are  often  called,  the  Gallinaceous  Birds 
— are  characterized  by  the  fact  that  the  upper  mandible  of  the 
bill  is  convex  and  vaulted  (Fig.  134),  and  has  a  membranous 
space  at  its  base,  in  which  the  nostrils  are  pierced.  The  nos- 
trils are  also  covered  by  a  cartilaginous  scale.  The  legs  are 
strong  and  muscular,  and  are  often  covered  with  feathers  as 
far  as  the  ankle-joint.  There  are  four  toes  (Fig.  134),  three 
in  front,  and  a  short  hind-toe  placed  on  a  higher  level  than  the 
others.  All  the  toes,  in  the  typical  members  of  the  order,  are 
provided  with  strong,  blunt  claws,  suitable  for  scratching. 
The  food  of  the  Rasores  consists  chiefly  of  hard  grains  and 
seeds,  and,  in  accordance  with  this,  they  have  a  large  crop, 
and  an  extremely  strong  and  muscular  gizzard.  They  gener- 
ally lay  their  eggs  upon  the  ground,  and  they  are  mostly 
polygamous,  each  male  having  several  mates.  The  Doves, 
however,  pair  for  life.  The  males  take  no  part  in  building 
the  nest  or  in  hatching  the  eggs ;  and  the  young  are  generally 
precocious,  being  able  to  run  about  and  provide  themselves 
with  food  from  the  moment  they  quit  the  egg.  The  wings 
are  usually  weak,  and  the  flight  feeble,  and  accompanied  with 
a  whirring  sound;  but  many  of  the  Pigeons  are  powerful 
flyers. 

The  order  Rasores  is  divided  into  two  very  well  marked 
sections  or  sub-orders,  called  respectively  the  Grattinacei  and 
Columbacei.  In  the  Gfallinacei  are  all  the  typical  forms  of 
the  order,  and  the  characters  of  this  section  are  therefore  the 
same  as  those  of  the  order  itself.  They  are  distinguished  from 


272 


VERTEBRATE  ANIMALS. 


the  Columbacei  mainly  by  being  less  fully  adapted  for  flight, 
their  bodies  being  much  heavier,  comparatively  speaking,  their 
legs  and  feet  stronger,  and  their  wings  shorter.  They  are  also 
generally  polygamous,  and  the  males  usually  possess  "  spurs," 
and  are  more  brilliantly  colored  than  the  females. 


FIG.  134.— Easores.    Bock-pigeon  (Colwmba  livid). 

The  leading  families  of  the  Gallinaceous  birds  are :  1.  The 
Tetraonidce  or  Grouse  family,  comprising  the  true  Grouse  and 
Black  Game  (Tetrao),  the  Ptarmigans  (Lagopus),  the  Ruffed 
Grouse  (J3onasa),  etc.  2.  The  Perdicidoe  or  Partridge  family, 
comprising  the  Partridges  (Perdix),  Quails  ( Coturnix\  Vir- 
ginian and  Mountain  Quails  ( Ortyx),  Crested  Quails  (LopTior- 
tyx),  etc.  3.  The  Phasianidce,  or  Pheasant  family,  comprising 
the  various  Pheasants  (Phasianus),  the  Domestic  and  Jungle 
fowls  (Gallus),  the  Turkeys  (Meleagris),  the  Guinea-fowls 
(Wumida),  and  the  Pea-fowl  (Pavo).  4.  The  Megapodidce, 
or  Mound-builders,  comprising  only  some  singular  Australian 
and  Indian  birds,  which  build  enormous  mounds,  in  which  they 
deposit  their  eggs.  5.  The  Cracidce,  or  Curassow  family, 


DIVISIONS   OF  BIRDS.  273 

comprising  the  large  South  and  Central  American  birds  known 
as  Curassows  and  Guans. 

The  Columbacei  comprise  the  Pigeons  and  Doves  (Fig.  134), 
and  they  are  separated  from  the  typical  Hasores  by  being 
much  more  fully  adapted  for  flight.  They  are  furnished  with 
strong  wings  and  are  good  flyers  ;  and,  in  place  of  being  ground- 
birds,  their  habits  are  to  a  great  extent  arboreal,  in  accordance 
with  which  the  feet  are  slender  and  are  adapted  for  perching. 
They  are  also  not  polygamous,  and  their  voice  is  of  a  much 
more  gentle,  soft,  and  melancholy  character.  (Hence  the  name 
of  Gemitores  applied  to  this  section,  while  the  Gallinacei  are 
called  the  Clamatores.)  Besides  the  true  Pigeons  and  Doves, 
this  sub-order  includes  also  the  remarkable  extinct  bird,  the 
Dodo,  which  was  of  gigantic  size,  comparatively  speaking,  and 
inhabited  the  island  of  Mauritius  up  to  the  commencement  of 
the  seventeenth  century. 

OKDEE  Y.  SCANSORES  (Lat.  scando,  I  climb). — The  order 
of  Scansores  or  Climbing  Birds  is  very  shortly  and  easily  de- 
fined, having  no  other  distinctive  and  exclusive  peculiarity 
except  the  fact  that  the  feet  have  four  toes,  of  which  two  are 
turned  backward  and  two  forward  (Fig.  135).  Of  the  two 
toes  which  are  turned  backward,  one  is  the  proper  hind-toe, 
and  the  other  is  the  outermost  toe.  This  arrangement  of 
the  toes  enables  the  Scansorial  birds  to  climb  with  great 
ease  and  readiness.  Their  powers  of  flight  are  usually  very 
moderate,  and  below  the  general  average,  and  their  food  con- 
sists of  insects  and  fruits  of  various  kinds.  Their  nests  are 
usually  made  in  the  hollows  of  old  trees,  but  some  (Cuckoos) 
have  the  remarkable  habit  of  depositing  their  eggs  in  the 
nests  of  other  birds.  They  are  never  polygamous,  and  the 
young  are  born  in  a  naked  and  helpless  condition. 

The  following  families  have  been  established  in  the  Scan- 
sores  :  1.  The  Cuculidce  or  Cuckoo  family,  comprising  the  true 
Cuckoos  and  some  allied  birds.  They  are  remarkable  for  the 
fact  that  many  of  them  are  "  parasitic,"  that  is  to  say,  they 
lay  their  eggs  in  the  nests  of  other  birds.  The  Yellow-billed 
Cuckoo  (C.  Americanus),  however,  of  the  United  States, 
builds  a  nest  for  itself  and  brings  up  its  own  young.  2.  The 
Picidce  or  Woodpecker  family,  comprising  many  familiar 
birds,  all  of  which  climb  and  run  up  trees  with  the  greatest 
facility.  They  live  mostly  on  insects,  which  they  catch  by 
darting  out  their  long,  worm-like,  barbed  tongue.  3.  The 
Psittacidce  or  Parrot  family,  comprising  the  true  Parrots,  the 


274  VERTEBRATE  ANIMALS. 

Cockatoos,  the  Lories,  the  Parrakeets,  and  the  Macaws.  They 
are  all  natives  of  hot  climates,  and  are  most  remarkable  for 
their  brilliant  plumage,  and  loud,  harsh,  and  grating  voices. 


FIG.  135.— Scansores.    Purple-capped  Lory  (Loriw  domicella). 

The  beak  (Fig.  135)  is  hooked,  and  is.  used  as  a  kind  of  third 
foot  in  climbing,  but  some  move  about  actively  on  the  ground. 
4.  The  Hhamphastidce  or  Toucans,  distinguished  by  their 
enormously  large  and  cellular  bills,  the  sides  of  which  are  ser- 
rated. They  live  in  deep  forests,  in  small  flocks,  and  are  con- 
fined to  tropical  America.  5.  The  Trogonidce  or  Trogons, 
which  inhabit  the  most  retired  recesses  of  the  forests  of  the 
intertropical  regions  of  both  hemispheres,  and  are  distin- 
guished by  their  resplendent  plumage. 

ORDER  VI.  INSESSOKES  (Lat.  insedeo,  I  sit  upon,  or  perch). 
— The  sixth  order  of  Birds  is  that  of  the  Insessores  or  Perchers, 
often  spoken  of  as  the  Passerine  Birds  (Lat.  passer,  a  sparrow). 


DIVISIONS   OF  BIRDS. 


275 


They  are  defined  by  Owen  as  follows :  "  Legs  slender,  short, 
with  three  toes  before  and  one  behind,  the  two  external  toes 
united  by  a  very  short  membrane  "  (Fig.  136,  A,  B). 

"  The  Perchers  form  by  far  the  most  numerous  order  of 
birds,  but  are  the  least  easily  recognizable  by  distinctive  char- 
acters common  to  the  whole  group.  Their  feet,  being  more 
especially  adapted  to  the  delicate  labors  of  nidification " 
(building  the  nest),  "have  neither  the  webbed  structure  of 
those  of  the  Swimmers,  nor  the  robust  strength  and  destruc- 
tive talons  which  characterize  the  feet  of  the  JBirds  of  Rapine^ 
nor  yet  the  extended  toes  which  enable  the  Wader  to  walk 
safely  over  marshy  soils  and  tread  lightly  on  the  floating  leaves 
of  aquatic  plants  ;  but  the  toes  are  slender,  flexible,  and  moder- 
ately elongated,  with  long,  pointed,  and  slightly-curved  claws. 


FIG.  136.— Insessores.  A,  Foot  of  Yellow  "Wagtail;  B,  Foot  ofWater  Ouzel;  C,  Oonirostral 
beak  (Hawfinch) ;  D,  Dentirostral  beak  (Shrike) ;  E,  Tenuirostral  beak  (Iluruniing-bird) : 
F,  Fissirostral  beak  (Swift). 

"  The  Perchers,  in  general,  have  the  females  smaller  and 
less  brilliant  in  their  plumage  than  the  males ;  they  always 
live  in  pairs,  build  in  trees,  and  display  the  greatest  art  in  the 
construction  of  their  nests.  The  young  are  excluded  in  a  blind 
and  naked  state,  and  are  wholly  dependent  for  subsistence 


276  VERTEBRATE  ANIMALS. 

during  a  certain  period  on  parental  care.  The  brain  arrives 
in  this  order  at  its  greatest  proportionate  size ;  the  organ  of 
voice  here  attains  its  utmost  complexity ;  and  all  the  charac- 
teristics of  the  bird,  as  power  of  flight,  melody  of  voice,  and 
beauty  of  plumage,  are  enjoyed  in  the  highest  perfection  by 
one  or  other  of  the  groups  of  this  extensive  and  varied  order." 
The  structure,  then,  of  the  feet  gives  the  definition  of  the 
order,  but  the  minor  subdivisions  are  founded  on  the  nature 
of  the  beak  ;  this  organ  varying  in  form  according  to  the  na- 
ture of  the  food,  which  may  be  "  small  or  young  birds,  carrion, 
insects,  fruit,  seeds,  vegetable  juices,  or  of  a  mixed  kind."  In 
accordance  with  this  character,  the  Insessores  have  been  di- 
vided into  four  great  sections,  as  follows : 

1.  Conirostres — in  which   the  bill  is    strong   and  on  the 
whole  conical,  broad  at  the  base  and  tapering  with  consider- 
able rapidity  to  the  point  (Fig.  136,  C).     The  upper  mandible 
is  not  markedly  toothed  at  its  lower  margin.     Good  exam- 
ples of  the  Conirostral  beak  are  to  be  found  in  the  common 
Sparrow,  Bullfinch,  Crow,  or  Hawfinch  (C).     The  greater  part 
of  the  Conirostres  are  omnivorous,  eating  any  thing  which 
may  come  in  their  way ;  but  some  are  granivorous,  subsisting 
upon  grains  and  seeds.     To  this  section  belong  the  Hornbills 
(JSuceridce),  the  Starlings  (Sturnidce\  the  Crows,  Jays,  and 
Magpies  (Corvidce),  the  Cross-bills  (Loxiadce),  and  the  nu- 
merous Finches,  Buntings,  Grosbeaks,  Tanagers,  and  Larks 
(Fringillidoe) . 

2.  Dentirostres. — The  birds  of  this  section  are  characterized 
by  the  fact  that  the  upper  mandible  of  the  beak  is  notched  or 
toothed  on  its  lower  margin  near  the  tip  (Fig.  136,  D).    They 
all  feed  upon  animal  food,  especially  upon  insects.     In  this 
section  are  the  Shrikes  (Laniidce),  the  Fly-catchers  (Muscica- 
pidce),  the  Thrushes  (Memlidce),  the  Tits  (Paridc^),  and  the 
Warblers  (Sylviadce). 

3.  Tenuirostres. — In   this    section   the   beak   is  long  and 
slender,  gradually  tapering  to  a  point  (Fig.  136,  E).    The  toes 
are  generally  very  long  and  slender,  especially  the  hinder  toe. 
Many  live  to  a  great  extent  upon  vegetable  juices,  and  among 
these  are  some  of  the  most  fragile  and  brightly-colored  of  all 
the  birds.     A  great  many,  however,  live  upon  insects,  either 
partially  or  entirely,  and  some  of  these  approach  nearly  to  the 
Dentirostres  in  many  of  their  characters.     Among  the  more 
important  groups  included  in  this  section  are  the  Creepers  and 
Wrens  (  Certhidce),  the  Honey-eaters  (Meliphagidce),  the  Hum- 
ming-birds (Trochilidce),  and  the  Hoopoes  (Upupinm). 


DIVISIONS  OF  BIRDS.  277 

4.  Fissirostres. — The  beak  in  the  Fissirostral  birds  (Fig. 
136,  F)  is  generally  short,  and  remarkably  wide  in  its  gape, 
and  the  opening  of  the  bill  is  protected  by  a  number  of 
bristles.  This  arrangement  is  in  accordance  with  the  habits 
of  the  Fissirostres,  the  typical  forms  of  which  live  upon  in- 
sects and  take  their  prey  upon  the  wing.  The  most  typical 
Fissirostres,  in  fact,  such  as  the  Swallows  and  Goat-suckers, 
fly  about  with  their  mouths  open,  and  the  insects  which  they 
catch  in  this  way  are  prevented  from  escaping,  partly  by  the 
bristles  which  border  the  gape,  and  partly  by  a  sticky  secretion 
within  the  mouth.  The  most  typical  Fissirostral  birds  are  the 
Swallows  and  Martens  (Sirundinidce),  the  Goat-suckers  ( Car 
primulgidce),  and  the  Swifts  ( Cypselidce) ;  but  to  these  the 
Bee-eaters  (Meropidce)  and  the  King-fishers  (Alcedinidce)  are 
usually  added. 

OKDER  VII.  RAPTOEES  (Lat.  rapto,  I  plunder). — The 
Birds  of  Prey  are  characterized  by  the  form  of  the  beak, 
which  is  adapted  for  tearing  animal  food  (Fig.  137,  B).  The 
upper  mandible  is  the  longest,  hooked  at  its  point,  "  strong, 
curved,  sharp-edged,  and  sharp-pointed,  often  armed  with  a 
lateral  tooth"  (Owen).  The  body  is  extremely  muscular;  the 


FIG.  13T.— Raptores.    A,  Foot  of  Peregrine  Falcon;  B,  Head  of  Buzzard. 

legs  are  robust,  short,  with  three  toes  in  front  and  one  behind ; 
all  the  toes  armed  with  strong,  curved,  crooked  claws  or  talons 
(Fig.  137,  A).  They  all  feed  upon  the  flesh  of  other  animals, 
which  they  either  kill  for  themselves  or  find  dead,  and  their 
flight  is  generally  extremely  rapid  and  powerful.  They  are 
not  polygamous,  and  the  female  is  larger  than  the  male.  They 
usually  build  their  nest  in  lofty  and  inaccessible  situations,  and 
seldom  lay  more  than  four  eggs.  The  young  are  hatched  in 
a  naked  and  helpless  condition. 
13 


278  VERTEBRATE  ANIMALS. 

The  Raptores  are  divided  into  two  sections — the  Nocturnal 
Birds  of  Prey,  which  hunt  at  night,  and  the  Diurnal  Birds  of 
Prey,  which  hunt  by  day.  In  the  former  section  is  only  the 
single  family  of  the  Owls  (StrigidcB),  in  which  the  eyes  are 
large,  and  are  directed  forward ;  while  the  plumage  is  exceed- 
ingly soft  and  loose,  so  as  to  render  their  flight  almost  noise- 
less. The  Owls  (Fig.  138)  hunt  their  prey  in  the  twilight  or 
on  moonlight  nights,  and  they  live  mostly  upon  field-mice  and 
small  birds,  but  they  will  also  eat  insects  and  frogs.  In  the 


A 
FIG.  138— A,  Foot  of  Tawny  Owl;  B,  Head-of  White  Owl. 


section  of  the  diurnal  Raptores  are  the  Falcons  and  Hawks, 
the  Eagles  and  the  Vultures.  In  all  these  the  eyes  are  smaller 
than  in  the  Owls,  and  are  placed  laterally,  and  the  plumage  is 
not  soft.  They  usually  possess  extraordinary  powers  of  flight. 
The  wings  are  long  and  pointed,  the  sternal  keel  is  greatly 
developed,  the  pectoral  muscles  are  of  large  size,  and  many  of 
them  exhibit  powers  of  locomotion  more  rapid  than  those  en- 
joyed by  any  other  members  of  the  animal  kingdom. 

Of  the  diurnal  Raptores,  America  has  many  examples,  and 
some  of  these  are  among  the  most  celebrated  members  of  the 
entire  order.  Besides  many  Hawks,  Buzzards,  and  Kites,  may 
be  especially  mentioned  the  Bald  Eagle,  the  Californian  Vul- 
ture, and  the  Condor.  The  Bald  or  White-headed  Eagle 
(Halietus  leucocephalus)  is  well  known  as  the  national  emblem 
of  the  United  States.  It  is  a  fine  and  courageous  bird,  and 
lives  to  a  great  extent  upon  fish,  which  it  either  catches  for 
itself,  or,  more  commonly,  wrests  forcibly  from  the  American 
Osprey.  The  Californian  Vulture  (  Cathartes  Calif ornianus) 
is  the  largest  of  the  Birds  of  Prey,  with  the  single  exception 


DIVISIONS  OF  BIRDS.  279 

of  the  Condor.  It  is  entirely  confined  to  the  Pacific  coast.  The 
Condor  (Sarcorhampus  gryphus)  has  a  stretch  of  wing  of 
from  12  to  14  feet,  and  is  usually  seen  soaring  in  majestic  cir- 
cles at  great  elevations,  rising,  it  is  said,  to  a  height  of  over 
20,000  feet.  It  inhabits  the  lofty  mountain-ranges  of  the 
Andes,  and  lays  its  eggs  at  a  height  of  from  10,000  to  15,000 
feet. 

ORDER  VIII.  SATJRTJRJS  (Gr.  saura,  lizard ;  our  a,  tail). — 
This  order  includes  only  the  single  extinct  bird,  the  Archceop- 
teryx,  which  has  been  found  in  the  Oolitic  rocks  of  Germany. 
The  Archceopteryx  was  about  as  big  as  a  common  Rook,  and 
shows  many  singular  points  of  resemblance  to  the  true  Rep- 
tiles. It  differs  from  all  living  birds  in  having  two  free  claws 
to  the  wing,  and  in  possessing  a  long,  lizard-like  tail.  Instead 
of  the  ploughshare-shaped  bone  which  terminates  the  tail  in 


FIG.  139.— Archaeopteryx.    Tail  and  detached  bones. 

living  birds  (Fig.  129,  B),  the  tail  in  the  ArcJiceopteryx  is  very 
long,  and  consists  of  about  twenty  distinct  and  separate  ver- 
tebrse,  each  of  which  supports  a  pair  of  quill-feathers.  The 
tail,  therefore,  except  for  the  presence  of  feathers,  must  have 
been  very  like  that  of  a  Lizard, 


MAMMALIA. 

CHAPTER    XXXI. 
CLASS  V.— MAMMALIA. 

THE  Mammalia  include  all  the  ordinary  quadrupeds,  and 
may  be  shortly  defined  as  comprising  Vertebrate  Animals  in 
which  some  part  or  other  of  the  skin  is  always  provided  with 
hairs,  and  the  young  are  nourished  for  a  longer  or  shorter 
time  by  means  of  a  special  fluid — the  milk — secreted  by  special 
glands — the  mammary  glands.  These  two  peculiarities  are 
of  themselves  sufficient  to  separate  the  Mammals  from  all 
other  classes  of  the  Vertebrate  sub-kingdom.  In  addition, 
however,  to  these  two  leading  characteristics,  the  following 
points  are  of  scarcely  less  importance : 

1.  The  skull  is  united  with  the  spinal  column  by  means  of 
two  articulating  surfaces  or  condyles,  instead  of  one,  as  in  the 
Reptiles  and  Birds. 

2.  The  lower  jaw  consists  of  two  halves,  each  composed 
of  a  single  piece,  and  united  in  front.     The  lower  jaw,  also,  is 
always  jointed  directly  with  the  skull,  and  there  is  no  quad- 
rate bone. 

3.  The  heart  consists — as  in  Birds — of  four  distinct  cham- 
bers, two  auricles  and  two  ventricles.    The  right  and  left  sides 
of  the  heart  are  completely  separated  from  one  another,  and 
there  is  never  any  direct  communication  between  the  blood 
sent  to  the  lungs  and  that  sent  to  the  body.    The  red  corpuscles 
of  the  blood  (Fig.  99,  a)  are,  in  the  great  majority  of  cases, 
in  the  form  of  circular  disks,  and  they  never  contain  any  inter- 
nal solid  particle  or  nucleus. 

4.  The  cavities  of  the  chest   (thorax)   and  abdomen  are 
separated  from  one  another  by  a  muscular  partition,  which  is 
called  the  midriff  or  diaphragm,  and  is  the  chief  agent  in  res- 
piration. 


MAMMALIA.  281 

5.  The  respiratory  organs  are  in  the  form  of  two  lungs, 
placed  in  the  chest,  and  never  communicating  with  air-recep- 
tacles situated  in  different  parts  of  the  body.  In  no  case  and 
at  no  period  of  life  are  gills  or  branchiae  present. 

As  regards  the  skeleton  of  the  Mammalia  it  is  not  neces- 
sary to  add  much  to  what  was  said  in  speaking  of  the  Verte- 
brata  generally.  With  few  exceptions,  the  spinal  column  is 
divisible  into  the  same  regions  as  in  man — namely,  the  neck 
or  cervical  region,  the  back  or  dorsal  region,  the  loins  or  lum- 
bar region,  the  sacral  region,  and  the  tail  or  caudal  region  (see 
Fig.  95).  In  spite  of  the  great  differences  observable  in  the 
length  of  the  neck  in  different  Mammals,  the  number  of  ver- 
tebrae which  form  the  cervical  region  is  extraordinarily  con- 
stant, being  almost  invariably  seven.  In  this  respect  the 
Giraffe,  which  is  the  longest-necked  of  Mammals,  agrees  with 
the  Whale,  which  can  hardly  be  said  to  have  a  neck  at  all. 
The  vertebrae  of  the  back  or  dorsal  region  are  mostly  thirteen 
in  number,  but  are  often  more.  In  man  there  are  only  twelve ; 
and  in  some  cases  there  are  only  eleven  or  ten.  The  lumbar 
vertebrae  are  usually  six  or  seven  in  number ;  five  in  man ; 
rarely  less  than  four.  The  sacral  vertebrae  are  usually  amalga- 
mated to  form  a  single  bone — the  sacrum — but  this  is  wanting 
in  the  Whales.  The  number  of  vertebrae  in  the  tail  or  caudal 
region  varies  from  four  to  as  many  as  five-and-forty,  and  they 
are  usually  freely  movable  upon  one  another.  The  thoracic 
cavity  or  chest  in  Mammals  is  always  enclosed  by  a  series  of 
ribs ;  the  number  of  which  varies  with  the  number  of  the  dor- 
sal vertebrae.  As  a  rule,  the  ribs  are  united  to  the  breastbone 
or  sternum  in  front,  not  by  bony  pieces,  as  in  birds,  but  by 
cartilages.  Only  the  front  ribs  reach  the  sternum,  and  these 
are  called  the  "  true  "  ribs ;  the  hinder  ribs  fall  short  of  the 
breastbone,  and  are  called  the  "  false  "  ribs.  The  sternum  is 
composed  of  several  pieces,  placed  one  behind  the  other,  but 
usually  amalgamated  to  form  a  single  bone.  It  is  usually  long 
and  narrow  in  shape,  and  is  only  rarely  furnished  with  any 
ridge  or  keel,  as  it  is  in  birds.  The  regular  number  of  limbs 
in  the  Mammals  is  four,  two  anterior  and  two  posterior;  and 
for  this  reason  the  Mammals  are  often  spoken  of  as  Quadru- 
peds. Some  Mammals,  however,  such  as  the  Whales  and 
Dolphins,  have  only  the  anterior  limbs,  and  many  of  the  Am- 
phibia and  Reptiles  walk  upon  four  legs.  As  regards  the 
structure  of  the  fore-limbs  (Fig.  96),  the  general  plan  of  con- 
formation is  the  same  as  described  in  treating  of  the  Verte- 


282  VERTEBRATE  ANIMALS. 

brata  generally  (p.  202).  The  shoulder-blade  or  scapula  is 
never  absent ;  and  the  coracoid  bone,  which  is  so  marked  a 
feature  in  the  Birds,  is  with  hardly  an  exception  amalgamated 
with  the  scapula.  The  clavicles  or  collar-bones  are  often  want- 
ing or  rudimentary,  but  in  no  Mammal  are  they  ever  united 
together  in  front  so  as  to  form  a  merry-thought  or  "  furculum." 
The  regular  number  of  fingers  is  five,  but  they  vary  from  one 
to  five,  the  middle  finger  being  the  longest  and  most  persist- 
ent of  all,  and  being  the  only  finger  left  in  the  Horse.  Prop- 
erly each  finger  consists  of  three  short  bones  or  phalanges, 
except  the  thumb,  which  has  two ;  but  this  rule  is  occasionally 
departed  from.  While  the  fore-limbs  are  never  wanting,  the 
hind-limbs  are  sometimes  absent,  as  in  the  Whales.  Generally 
speaking,  however,  the  posterior  limbs  are  present,  and  the 
pelvic  arch  has  much  the  same  structure  as  in  man.  The  foot 
— like  the  hand — consists  regularly  of  five  digits,  but  it  is  sub- 
ject to  the  same  abortion  of  parts,  as  we  shall  see  hereafter. 

The  great  majority  of  Mammals  possess  teeth,  but  these 
are  only  present  in  the  embryo  of  the  whalebone  Whales,  and 
are  altogether  wanting  in  the  scaly  and  great  Ant-eaters.  The 
teeth  are  also  almost  invariably  implanted  in  distinct  sockets 
in  the  jaw.  Some  Mammals  have  only  a  single  set  of  teeth  ; 
but  in  most  cases  the  young  Mammal  possesses  a  set  of  what 
are  called  the  milk-teeth  or  deciduous  teeth,  which  is  ultimate- 
ly replaced  by  a  second  set,  constituting  the  permanent  teeth. 
No  Mammal  has  ever  more  than  two  sets  of  teeth.  In  man, 
and  in  many  other  Mammals,  the  teeth  are  divisible  into  four 
groups,  which  differ  from  one  another  in  position,  appearance, 
and  function.  These  are  termed  respectively  the  incisors,  ca- 
nines, prcemolars,  and  molars.  It  is  impossible  to  describe 
fully  which  teeth  come  under  each  of  these  heads  without  en- 
tering into  unnecessary  details  as  to  the  structure  of  the  jaws. 
It  must  be  sufficient  here  to  point  out  the  general  characters 
and  position  of  these  groups  in  a  good  illustrative  example, 
such  as  one  of  the  higher  Apes  (Fig.  140).  The  incisors  (i) 
vary  greatly  in  size  and  number,  but  they  are  always  placed 
in  the  front  of  the  mouth,  and  are  the  teeth  which  are  used  in 
simply  biting  or  dividing  the  food.  The  canine  or  eye-tooth 
(c)  is  generally  larger  or  more  pointed  than  the  other  teeth. 
The  canines  are  sometimes  wanting,  or  are  sometimes  present 
in  one  jaw  and  not  in  the  other ;  but  there  are  never  more 
than  four  altogether — that  is  to  say,  one  in  each  jaw  on  each 
side.  The  prremolars  and  molars  (pm  and  m)  are  the  so-called 
"  back-teeth,"  and  they  vary  a  good  deal  in  number  and  function, 


MAMMALIA.  283 


being  sometimes  adapted  for  cutting  the  food,  but  more  usual- 
ly for  chewing  and  grinding  it  down. 


FIG.  140. — Teeth  of  the  right  side  of  the  lower  jaw  of  the  Chimpanzee  (after  Owen),    i  In- 
cisors ;  c  Canine  tooth ;  pm  Prseraolars ;  m  Molars. 

All  these  kinds  of  teeth  are  not  necessarily  present,  and 
the  teeth  constitute  most  important  characters  for  separating 
the  various  orders  of  Mammals  from  one  another.  For  this 
reason  it  is  usual  to  express  the  number  of  the  teeth  in  any 
particular  animal  by  an  arithmetical  formula,  called  the  dental 
formula.  For  example,  the  formula  for  the  portion  of  the 
jaw  of  the  Chimpanzee  figured  above  (Fig.  140)  would  be  as 
follows : 

i  2 ;  c  1 ;  pm  2 ;  m  3. 

But  this  is  only  one  half  of  the  lower  jaw,  and  the  dental  for- 
mula must  include  both  sides,  so  that  it  would  be : 

i  2 — 2 ;  c  I — 1 ;  pm  2—2 ;  m  3—3. 

That  this  would  be  the  formula  is  at  once  evident,  when  it  is 
remembered  that  the  two  sides  of  the  jaw  of  course  contain 
exactly  the  same  teeth.  Still,  the  formula  as  given  above  only 
includes  the  lower  jaw,  and  to  render  it  perfect  it  must  take 
in  the  teeth  of  the  upper  jaw  as  well.  This  is  effected  by 
placing  the  figures  in  two  rows  separated  by  short  lines,  all 
the  figures  in  the  upper  row  referring  to  the  upper  jaw,  and 
those  in  the  lower  row  to  the  lower  jaw;  the  short  dashes  be- 
tween the  figures  of  each  row  still  indicating  the  teeth  on  the 
two  sides  of  the  mouth.  The  complete  formula  would  there- 
fore run  as  follows : 


284  VERTEBRATE  ANIMALS. 

.2—2        1—1  2—2         3—3 


In  this  way  the  dentition  —  that  is  to  say,  the  number  and  ar- 
rangement of  the  teeth  —  can  be  presented  in  a  manner  which 
can  be  instantly  recognized  by  the  eye.  It  must  be  remem- 
bered, however,  that  the  formula  seldom  exhibits  the  regular- 
ity of  the  one  of  the  Chimpanzee  given  above.  The  teeth 
are  not  necessarily  the  same  in  both  jaws,  and  in  many  cases 
some  may  be  altogether  wanting.  To  show  this  there  is  sub- 
joined the  dental  formula  of  a  typical  Ruminant  animal,  such 
as  a  sheep  : 

.0—0        0—0  3—3         3—3 


33       11  3=3 

From  this  formula  it  will  be  seen  that  the  sheep  has  32  teeth 
in  both  jaws  taken  together.  The  upper  incisors  and  canines 
are  wanting,  and  there  are  three  praemolars  and  three  molars 
on  each  side  of  the  upper  jaw.  In  the  lower  jaw  there  are 
six  incisors,  two  canines,  and  the  same  number  of  prasmolars 
and  molars  as  in  the  upper  jaw. 

As  regards  the  digestive  system  of  Mammals,  the  alimen- 
tary canal  and  digestive  glands  have  on  the  whole  the  same 
general  structure  and  arrangement  as  in  man  (pp.  203,  204). 
Some  very  remarkable  modifications,  however,  in  the  structure 
of  the  stomach  and  in  the  termination  of  the  intestine  occur 
in  certain  Mammals  ;  but  these  will  be  noticed  in  speaking  of 
the  orders  in  which  they  occur. 

The  cavity  of  the  abdomen  in  Mammals  is  always  separated 
from  that  of  the  thorax  by  a  complete  muscular  partition  —  the 
diaphragm.  The  abdomen  contains  the  greater  part  of  the 
alimentary  canal,  the  liver,  pancreas,  kidneys,  and  other  or- 
gans. The  thorax  contains  chiefly  the  heart  and  lungs.  The 
heart  is  contained  in  a  membranous  sac  —  the  pericardium,  and 
consists  of  two  auricles  and  two  ventricles.  The  heart  con- 
sists functionally  of  two  sides,  each  having  an  auricle  and  a 
ventricle,  which  communicate  with  one  another  by  apertures, 
so  guarded  by  valves  that  the  blood  can  pass  from  the  auricle 
into  the  ventricle,  but  not,  under  ordinary  circumstances,  from 
the  ventricle  to  the  auricle.  There  is  in  the  adult  no  direct 
communication  between  the  two  sides  of  the  heart.  The 
course  of  the  circulation  is  indicated  in  the  subjoined  diagram, 
and  is  shortly  as  follows  :  The  venous  blood,  which  has  become 
impure  by  passing  through  the  tissues,  is  returned  by  the 
great  veins  to  the  right  auricle,  from  which  it  passes  into  the 


MAMMALIA. 


285 


right  ventricle.  From  here  it  is  driven  through  a  great  vessel, 
called  the  pulmonary  artery,  to  the  lungs,  where  it  is  submitted 
to  the  action  of  the  air,  and  becomes  arterial  blood.  It  is  then 
returned  to  the  heart  by  a  series  of  vessels,  called  the  pulmo- 
nary veins,  and  is  poured  into  the  left  auricle,  from  which  it 
passes  into  the  left  ventricle.  From 
the  left  ventricle  it  is  propelled  to 
all  parts  of  the  body  by  a  great 
systemic  vessel,  which  is  called  the 
aorta  (Fig.  141). 

The  lungs  of  Mammals  are  two 
in  number,  and  differ  from  those  of 
Birds  in  being  freely  suspended  in 
membranous  bags.  They  are  spongy 
and  cellular  throughout,  and  they 
never  communicate  by  apertures  on 
their  surface  with  air-sacs  placed  in 
different  parts  of  the  body. 

The  nervous  system  of  Mammals 
is  chiefly  remarkable  for  the  great 
proportionate  development  of  the 
brain,  as  compared  with  the  spinal 
cord. 

In  the  higher   Mammals,  also, 
the  two  halves  (hemispheres)  of  the 
brain   proper   (cerebrum)   are   con-   FIG.  141.— Diagram  of  the  circulation 
nected  together  by  a  great  band  or 

bridge  of  nervOUS  tiSSUe,  COnstltut- 

ing  what  is  known  as  the  corpus 
callosum.  This  structure  is  not  a 
conspicuous  feature  in  the  two  low- 
est orders  of  the  Mammalia.  The 
senses,  as  a  rule,  attain  great  per- 
fection in  the  Mammals;  and  the 
only  sense  which  can  ever  be  said  to  be  entirely  wanting  is 
that  of  sight.  Eyes,  however,  are  always  present,  though 
they  may  be  rudimentary ;  and  in  those  Mammals  which  are 
said  to  be  "  blind,"  it  is  not  generally  that  the  eyes  are  want- 
ing, but  that  the  skin  passes  unbrokenly  over  the  eyeball,  or 
the  optic  nerve  is  degenerated.  Even  in  these  cases,  however, 
it  is  not  impossible  that  there  maybe  some  perception  of  light 
through  the  skin.  An  external  ear  for  collecting  sounds  is 
usually  present;  but  it  is  wanting  in  the  Whales  and  Dol- 
phins, and  in  some  of  the  Seals. 


black,  those  containing  arterial 
blood  are  left  white.)  a  Eight 
auricle;  v  Eight  ventricle ;  p  Pul- 
monary artery  carrying  venous 


blood  to  the  lungs ;  pv  Pulmonary 
veins  carrying  arterial  blood  from 
the  lungs ;  af  Left  auricle ;  t/  Left 


ventricle ;  &  Aorta  carrying  arte- 
rial blood  to  the  body ;  c  Vena  cava 
carrying  venous  blood  to  the  heart 


286  VERTEBRATE  ANIMALS. 

The  skin  is  invariably  furnished  over  a  greater  or  less  part 
of  its  surface  with  the  epidermic  appendages  known  as  hairs, 
which  differ  from  feathers  chiefly  in  not  splitting  up  as  they 
are  produced.  In  the  scaly  Ant-eater  (Manis),  the  hairs  are 
aggregated  together  so  as  to  form  horny  scales ;  and  in  the 
Hedge-hog,  Porcupine,  and  other  animals,  many  of  the  hairs 
are  developed  into  long  spines  or  prickles.  In  other  cases, 
again,  as  in  the  Armadillos,  the  skin  is  more  or  less  covered 
by  an  armor  of  bony  plates.  The  only  apparent  exception  to 
the  universal  presence  of  hair  on  some  part  or  other  of  the  in- 
tegument of  all  Mammals  is  constituted  by  the  true  Cetaceans 
(Whales  and  Dolphins),  many  of  which  are  without  hair  when 
grown  up.  Some,  however,  such  as  the  Whales,  have  a  few 
bristles  in  the  neighborhood  of  the  mouth,  even  when  adult. 
And  the  Dolphins,  which  are  totally  hairless  when  grown 
up,  exhibit  tufts  of  hair  upon  the  muzzle  before  they  are 
born. 

The  young  Mammal  is  always  born  in  a  helpless  condition, 
and  is  nourished  for  a  longer  or  shorter  time  by  means  of  the 
milk  of  the  mother.  The  milk  is  secreted  by  special  organs, 
called  the  mammary  glands,  which  are  present  in  both  sexes, 
but  are  normally  undeveloped  in  the  male.  The  number  and 
position  of  the  mammae  vary  a  good  deal  in  different  cases, 
but  they  are  always  placed  on  the  lower  surface  of  the  body, 
and  their  ducts  almost  always  open  upon  a  special  eminence, 
called  the  teat  or  nipple.  In  one  or  two  cases,  however,  the 
mammary  glands  open  by  simple  slits  in  the  skin  of  the  abdo- 
men, and  not  by  distinct  nipples.  In  ordinary  Mammals  the 
milk  is  obtained  by  voluntary  suction  on  the  part  of  the  young, 
but  in  the  Marsupials  (Kangaroos,  Opossums,  etc.)  the  milk  is 
forced  into  the  mouth  of  the  young  animal  by  the  action  of  a 
special  muscle. 

So  much  difference  of  opinion  obtains  as  to  the  best  foun- 
dation upon  which  to  establish  a  division  of  the  Mammalia 
into  great  primary  sections,  that  it  has  been  thought  advisable 
to  leave  this  subject  wholly  out  of  consideration.  For  our 
present  purpose  it  is  enough  to  adopt  the  old  classification  of 
Mammals  into  the  two  great  divisions  of  the  Placental  and 
Non-placental  forms.  In  the  Placental  Mammals  the  young 
is  nourished  within  the  body  of  the  mother  by  means  of  a 
structure  called  the  placenta,  or  "  afteH-birth,"  through  which 
the  nutrient  materials  of  the  mother's  blood  reach  the  young. 
In  consequence  of  this,  the  young  of  the  Placental  Mammals 
can  be  retained  within  the  body  for  a  considerable  period,  and, 


MAMMALIA.  287 

when  born,  they  are  able  to  obtain  their  natural  food — the 
milk — by  their  own  exertions.  In  the  Non-placental  Mam- 
mals, 011  the  other  hand,  the  young  are  born  at  an  extremely 
early  period  of  their  development,  before  there  is  any  necessity 
that  a  placenta  should  be  formed  for  the  nourishment  of  the 
foetus.  In  these  cases,  therefore,  the  young  when  born  are 
much  more  immature  and  helpless  than  in  the  case  of  the 
Placental  Mammals.  So  helpless  are  they,  that  they  are  even 
unable  to  suck,  and  have  in  most  cases  to  be  fixed  by  the 
mother  herself  upon  the  teats,  while  the  milk  is  forced  into 
their  mouths  by  a  muscle  which  is  spread  over  the  mammary 
gland.  Adopting  these  primary  sections  as  practically  suf- 
ficient in  an  elementary  work,  the  whole  class  of  the 
Mammalia  may  be  divided  into  the  following  fourteen 
orders : 

DIVISION  A. — APLACENTAL  MAMMALS. 

Order  1. — Monotrcmata. 
Order  2. — Marsupialia. 

DIVISION  B. — PLACENTAL  MAMMALS. 
Order     3.— Edentata. 
Order    4. — Sirenia. 
Order     5. — Cetacea. 
Order     6. —  Ungulata. 
Order     7. — Hyracoidea. 
Order     8. — Proboscidea. 
Order     9. — Carnivora. 
Order  10. — Rodentia. 
Order  11. — Cheiroptera. 
Order  12. — Insectivora. 
Order  13. — Quadrumana. 
Order  14. — Bimana. 


CHAPTER  XXXII. 
ORDERS    OF    MAMMALIA. 

ORDER  I.  MONOTREMATA  (Gr.  monos,  single ;  trema,  aper- 
ture).— The  first  and  lowest  order  of  the  Mammals — that  of 
the  Monotremata — comprises  only  two  very  remarkable  ani- 
mals, both  of  which  are  exclusively  confined  to  New  Holland. 
These  are  the  Duck-mole  (  Ornithorhynchus)  and  the  Porcupine 
Ant-eater  (Echidna).  The  Monotremata  are  essentially  charac- 
terized by  the  fact  that,  as  in  Birds,  the  termination  of  the  in- 
testine opens  into  a  common  chamber  or  cloaca,  which  receives 
also  the  ducts  of  the  urinary  and  reproductive  organs.  The 
jaws  are  destitute  of  true  teeth ;  but  the  Ornithorhynchus 
has  a  kind  of  beak,  like  the  bill  of  a  duck,  furnished  with 
small  horny  plates,  which  act  as  teeth.  The  pectoral  arch, 
which  supports  the  fore-limbs,  resembles  that  of  Birds  in 
several  respects,  but  especially  in  the  fact  that  the  coracoid 
bones  are  distinct,  and  are  not  amalgamated  with  the  shoulder- 
blade.  There  is  no  pouch  developed  on  the  abdomen  of  the 
females,  but  there  are  the  so-called  "  marsupial  bones."  These 
are  two  small  bones  which  arise  from  the  front  of  the  pelvis. 
They  are  really  to  be  regarded  as  formed  by  a  conversion  into 
bone  of  the  tendons  of  one  of  the  muscles  of  the  abdomen. 
There  are  no  external  ears.  The  mammary  glands  have  no 
nipples,  and  the  young  are  said  to  be  devoid  of  a  placenta. 

The  Duck-mole  (Fig.  142)  is  one  of  the  most  extraordinary 
of  Mammals,  and  is  found  inhabiting  the  rivers  and  lakes  of 
Australia  and  Tasmania.  The  body  resembles  that  of  a  small 
otter,  and  is  covered  with  a  short  brown  fur.  The  tail  is 
broad  and  flattened,  and  the  jaws  are  sheathed  with  horn,  so 
as  to  form  a  flattened  beak,  very  like  the  bill  of  a  duck.  The 
legs  are  short,  furnished  with  five  toes  each,  and  webbed,  so 
that  the  animal  swims  with  great  facility.  Their  food  consists 


ORDERS  OF  MAMMALIA.  289 

chiefly  of  aquatic  insects  and  mollusks,  and   they   make  very 
extensive  burrows  in  the  banks  of  streams. 


FIG.  142.— Monotremata.    Duck  -mole  (Ornitliorhynchus  paradoxus). 
(After  Waterhouse.) 

The  other  member  of  the  Monotremata  is  the  Porcupine 
Ant-eater  or  Echidna,  which  is  not  unlike  a  large  hedgehog 
in  appearance.  The  snout  is  very  long,  and  is  enclosed  in  a 
continuous  skin  till  close  upon  its  extremity,  where  there  is  a 
small  aperture  for  the  protrusion  of  a  long  and  flexible  tongue. 
There  are  no  teeth,  nor  any  organs  to  act  as  teeth.  The  feet 
have  five  toes  each,  and  are  furnished  with  strong  digging- 
claws,  but  the  toes  are  not  webbed.  The  skin  is  covered  with 
strong  prickly  spines  interspersed  with  bristly  hair.  The 
Echidna  measures  from  fifteen  to  eighteen  inches  in  length, 
and  is  a  nocturnal  animal.  It  lives  in  burrows,  and  feeds 
upon  insects,  which  it  captures  by  protruding  its  long,  sticky 
tongue. 

ORDER  II.  MARSUPIALIA. — The  name  of  Marsupials  is  de- 
rived from  the  fact  that  the  females  of  this  order  are  mostly 
furnished  with  an  abdominal  pouch  or  marsupium,  within 
which  the  nipples  are  situated.  When  born,  the  young  are 
placed  by  the  mother  within  this  pouch,  where  they  adhere  to 
the  teats,  and  can  be  carried  about  without  injury.  Even 
when  further  advanced  in  their  development,  the  younor  often 
betake  themselves  to  the  shelter  of  the  marsupium.  The  so- 
called  "marsupial  bones"  are  present,  and  as  they  spring 
from  the  front  of  the  pelvis  they  no  doubt  serve  to  support  the 
pouch ;  but  this  cannot  be  their  sole  use,  as  they  exist  in  the 
males,  and  also'  in  the  Monotremes,  in  whom  there  is  no  pouch. 
All  Marsupials  possess  teeth,  and  the  pectoral  arch  has  now 
the  same  form  as  in  the  higher  Mammals,  the  coracoid  bones 


290 


VERTEBRATE  ANIMALS. 


being  now  amalgamated  with  the  shoulder-blade.     The  intes- 
tine does  not  terminate  in  a  cloaca. 

Though  the  Marsupialia  form  an  extremely  natural  order, 
sharply  separated  from  the  other  Mammals,  they  include  a 
large  number  of  varied  forms.  In  fact,  this  order,  from  its 
being  the  almost  exclusive  possessor  of  a  continent  so  large  as 
Australia,  has  to  discharge,  in  the  general  economy  of  nature, 
functions  which  are  elsewhere  performed  by  several  orders. 
As  regards  their  geographical  distribution,  with  the  single 


FIG  148.— Marsupialia.    The  Koala  or  Kanparoo-bear  (Pkascolarctos  cinereus). 
(After  Gould.) 

exception  of  the  family  Didelphidce  (the  true  Opossums),  the 
whole  order  of  the  Marsupials  is  exclusively  confined  to  Aus- 
tralia, Van  Diemen's  Land,  New  Guinea,  and  the  adjacent 
islands. 

The  Marsupials  may  be  primarily  divided  into  the  vege- 
table-eating and  rapacious  or  carnivorous  forms— the  former 
characterized  by  the  absence  or  rudimentary  condition  of  the 
canine  teeth,  the  molars  having  broad,  grinding  crowns; 
while  in  the  latter  there  are  well-developed  canines,  and  the 
molars  are  not  adapted  for  grinding.  Of  the  vegetable-eating 
forms,  the  best  known  are  the  Kangaroos  (Macropodidce\ 
distinguished  by  the  remarkable  disproportion  between  the 


ORDERS  OF  MAMMALIA.  291 

hind  and  fore  limbs,  the  former  being  by  far  the  longest  and 
strongest.  By  their  long  hind-legs,  assisted  by  a  powerful 
tail,  the  Kangaroos  can  perform  astonishing  jumps,  and,  in 
fact,  leaping  is  their  mode  of  progression  when  pursued. 

The  typical  Kangaroos  live  on  the  great  grassy  plains  of 
Australia ;  but  the  Tree  Kangaroos  spend  a  great  part  of 
their  time  in  trees,  and  the  Rock  Kangaroos  affect  mountainous 
districts.  The  Kangaroo-bear  or  Native  Sloth  (Phascolarc-" 
tos  cinereus,  Fig.  143)  has  no  tail,  and  has  the  body  covered 
with  a  short,  dense  fur,  while  the  ears  are  tufted.  The  fore- 
feet can  be  used  as  hands,  and  the  toes  are  all  furnished  with 
strong,  curved  claws.  It  is  a  harmless,  nocturnal  animal,  and 
spends  most  of  its  existence  in  trees.  The  typical  group, 
however,  of  the  vegetable-eating  Marsupials  is  that  of  the 
Phalangers,  comprising  a  large  number  of  small  animals  which 
live  in  trees,  and  generally  possess  a  prehensile  tail.  The 
most  familiar  example  is  the  Australian  "  Opossum  "  (PTialan- 
gista  vulpina),  which  is  largely  hunted  by  the  natives.  In 
the  so-called  "flying"  Phalangers,  again,  the  tail  is  not  pre- 
hensile, and  the  animal  takes  extensive  leaps  from  tree  to 
tree,  by  means  of  a  fold  of  skin  which  stretches  between  the 
body  and  the  fore  and  hind  limbs. 

Of  the  carnivorous  Marsupials,  the  Bandicoots  (Perameles), 
the  Native  Devil  (Dasyurus),  the  Native  Tiger  (Thylacinus), 
and  the  American  Opossums  (Didelphidce),  may  be  mentioned. 
The  Bandicoots  are  little,  rabbit-like  Australian  animals,  which 
live  upon  insects,  and  seem  to  fill  the  place  held  in  the  Old 
World  by  the  Hedgehogs  and  Shrew-mice.  The  Native  Devil 
and  Thylacine,  though  both  of  comparatively  small  size,  are 
extremely  ferocious,  and  do  much  mischief  to  the  flocks  of  the 
Tasmanian  colonists.  About  twenty  species  of  DidelphidoB 
are  known,  and  they  are  all  exclusively  confined  to  the  Ameri- 
can Continent.  They  are  all  of  small  size,  have  prehensile 
tails,  and  mostly  live  among  trees.  The  best-known  species 
is  the  Virginian  Opossum  (Didelphys  Virginiana). 

OEDER  III.  EDENTATA  (Lat.  e,  without ;  dens,  tooth). — 
This  order  of  Placental  Mammals  comprises  the  Ant-eaters, 
Armadillos,  and  Sloths,  and  is  characterized  by  the  fact  that 
the  teeth  are  not  covered  with  enamel,  have  no  complete 
roots,  and  are  never  replaced  by  a  second  set.  Further,  in 
none  of  the  Edentates  are  there  any  central  incisor  teeth,  and 
in  all  but  one  there  are  no  incisors  at  all.  In  two  genera  only 
are  there  no  teeth ;  so  that  the  name  Edentata  is  not  a  very 


292  VERTEBRATE  ANIMALS. 

appropriate  one.     In  all,  the  toes  are  furnished  with  long  and 
powerful  claws. 

The  Edentata  admit  of  division  into  two  sections,  accord- 
ing as  they  live  upon  a  vegetable  diet  and  live  in  trees,  or  are 
carnivorous  and  live  upon  or  below  the  ground.  In  the  first 
section  are  only  the  Sloths  (Bradypodidce) ,  which  are  exclu- 
sively confined  to  South  America,  inhabiting  the  vast  primeval 
forests  of  this  continent.  They  are  in  every  way  adapted  for 
an  arboreal  life,  and  are  "  destined  to  be  produced,  to  live,  and 
to  die  on  trees."  They  are  excessively  awkward  when  upon 
the  ground ;  but  the  feet  are  furnished  with  extremely  long, 
curved  claws,  so  that  the  animal  is  enabled  to  move  about 
freely,  suspended  back  downward  from  the  branches  of  the 


FIG.  144.— Edentata.    (Chlamyphorus  triwcatw.) 

trees.  The  Armadillos  (Dasypodidce)  are  also  exclusively 
confined  to  South  America ;  but  they  are  carnivorous,  burrow- 
ing animals,  and  are  furnished  with  strong  digging-claws. 
The  upper  surface  of  the  body  is  covered  with  a  kind  of  armor, 
formed  of  hard,  bony  plates  or  shields,  which  are  united  at 
their  edges  (Fig.  144).  Most  of  them  can  roll  themselves  up 
into  a  ball,  and  they  can  all  bury  themselves  in  the  ground 
when  pursued. 

The  remaining  South  American  Edentates  are  the  hairy 
Ant-eaters,  of  which  the  best  known  is  the  great  Ant-eater 
(Myrmecophaga  jubata).  The  body  in  this  family  is  covered 
with  hair,  the  tail  is  long,  and  the  teeth  are  altogether  want- 
ing. They  feed  chiefly  upon  ants  and  termites,  which  they 


ORDERS  OF  MAMMALIA.  293 

catch  by  protruding  their  long  and  sticky  tongues,  having 
previously  broken  into  the  nests  by  means  of  their  strong, 
curved  claws. 

The  Edentata  are  represented  in  the  Old  World  by  only 
two  genera.  One  of  these  is  the  genus  Manis,  comprising 
the  scaly  Ant-eaters  or  Pangolins,  which  are  exclusively  con- 
fined to  Asia  and  Africa.  In  these  singular  animals  the  body 
and  tail  are  covered  by  a  flexible  armor,  composed  of  horny 
plates  or  scales  overlapping  like  the  tiles  of  a  roof.  The 
other  genus  is  Orycteropus,  comprising  only  the  so-called 
Ground-hog  of  South  Africa ;  which  also  lives  upon  insects, 
and  burrows  by  means  of  its  strong  digging-claws. 

As  regards  the  geographical  distribution  of  the  Edentata, 
it  is  to  be  remembered  that  the  order  has  a  very  limited  range 
at  the  present  day.  The  true  Ant-eaters,  the  Armadillos, 
and  the  Sloths,  are  exclusively  confined  to  South  America,  in 
which  country  a  group  of  gigantic  extinct  Edentates  existed 
in  the  later  portion  of  the  Tertiary  epoch.  The  scaly  Ant- 
eater  is  common  to  Asia  and  Africa ;  and  the  Ground-hog  is 
confined  to  South  Africa. 

OKDEE,  IV.  SIKENIA  (Gr.  seiren^  a  Mermaid). — This  order 
comprises  only  certain  large  marine  Mammals,  known  as  Du- 
gongs  and  Manatees,  which  were  long  classed  with  the  Whales 
and  Dolphins  (Cetaced).  They  agree  with  the  Whales  in  the 
adaptation  of  the  body  to  an  aquatic  life,  especially  in  the 
facts  that  the  anterior  limbs  are  converted  into  swimming- 
paddles,  the  hind-limbs  are  wholly  wanting,  and  the  hinder 
end  of  the  body  forms  a  powerful  caudal  fin,  which  is  placed 
so  as  to  strike  the  water  horizontally,  and  not  vertically  as  in 
Fishes.  They  differ  from  the  Cetacea  in  having  the  nostrils 
placed  at  the  anterior  part  of  the  head,  arid  in  having  molar 
teeth  with  flat  crowns,  adapted  for  a  vegetable  diet.  Fleshy 
lips  are  present,  the  upper  one  usually  with  a  mustache,  and 
the  skin  is  covered  with  scanty  bristles.  The  head  is  not  dis- 
proportionately large  as  compared  with  the  body,  and  there  is 
a  tolerably  distinct  neck.  They  are  vegetable-eaters,  feeding 
chiefly  upon  sea-weeds,  and  haunting  the  mouths  of  rivers  and 
estuaries. 

The  only  existing  Sirenia  are  the  Manatee  (Manatus)  and 
the  Dugong  (Halicore),  often  called  "  Sea-cows."  The  Man- 
atees are  found  on  the  east  coast  of  America,  and  on  the  west 
coast  of  Africa.  They  are  large,  awkward  animals,  attaining 
a  length  of  from  eight  to  ten  or  fifteen  feet,  and  their  flesh  is 


294  VERTEBRATE  ANIMALS. 

said  to  be  very  palatable  and  wholesome.  The  Dugongs  (Fig. 
145)  differ  little  in  appearance  and  habits  from  the  Manatees. 
They  are  found  on  the  coasts  of  the  Indian  Ocean  and  the 
north  coast  of  Australia,  and  are  often  killed  and  eaten.  They 
attain  a  length  of  from  eighteen  to  twenty  feet.  The  bones 
of  the  skeleton  are  remarkable  for  their  extreme  hardness  and 
density. 


FIG.  145.— Sirenia.    The  Dugong  (ffalicore  Indices). 

Besides  these  living  forms,  the  Sirenia  were  represented 
by  a  gigantic  species  which  formerly  inhabited  Behring  Island 
on  the  coast  of  Kamtchatka.  This  animal  was  described  by  a 
M.  Steller  who  accompanied  Behring  on  his  second  expedition, 
and  he  named  it  Rhytina.  This  enormous  animal  attained  a 
length  of  twenty-five  feet,  and  a  circumference  of  twenty  feet, 
and  it  appears  to  have  been  completely  exterminated,  no  spe- 
cimen having  been  seen  for  two  centuries. 

ORDER  V.  CETACEA  (Gr.  fotos,  a  Whale). — This  order 
comprises  the  Whales,  Dolphins,  and  Porpoises,  and  it  is 
characterized  by  the  complete  adaptation  of  its  members  to  a 
watery  life.  The  body  is  completely  fish-like  in  form,  the  fore- 
limbs  are  converted  into  swimming-paddles,  and  the  hind- 
limbs  are  completely  wanting ;  while  the  hinder  end  of  the 
body  forms  an  extremely  powerful,  horizontal  caudal  fin. 
Sometimes  there  is  a  dorsal  fin  as  well.  The  nostrils  may  be 
single  or  double,  but  always  are  placed  on  the  top  of  the  head, 
constituting  the  "  blow-hole."  The  body  is  very  sparingly 
furnished  with  hairs,  or  is  wholly  without  them  in  the  adult. 
The  head  is  generally  of  disproportionately  large  size  as  com- 
pared with  the  body,  and  is  rarely  separable  from  the  trunk 
by  any  distinct  constriction  or  neck.  There  is  no  sacrum,  and 
the  pelvis  is  only  represented  in  a  rudimentary  form.  Lastly, 
the  adult  is  either  wholly  destitute  of  teeth,  or  possesses  only 


ORDERS  OF  MAMMALIA.  295 

a  single  set,  which  are  always  conical  in  shape,  and  are  never 
divisible  into  distinct  groups.  All  the  true  Cetacea  are  car- 
nivorous, living  upon  animal  food. 

Chief  among  the  Cetaceans  in  importance  and  zoological 
interest  are  the  Whalebone  Whales  (Balcenidce),  in  which 
the  adult  is  destitute  of  teeth,  though  the  young  whale  pos- 
sesses teeth  which  never  cut  the  gum.  The  place  of  teeth  is 
taken  by  a  series  of  transverse  plates  of  whalebone  or  baleen, 
which  are  used  as  a  kind  of  screening  apparatus  or  filter  to 
separate  from  the  sea-water  the  minute  Mollusks  and  Jelly- 
fishes  upon  which  these  enormous  animals  live.  The  most 
important  member  of  this  family,  from  a  commercial  point  of 
view,  is  the  Greenland  Whale  (JBalcena  mysticetus),  which 
yields  most  of  the  whale-oil  and  whalebone  of  commerce.  The 
Greenland  Whale  attains  a  length  of  from  forty  to  sixty  feet, 
and  of  this  enormous  length  about  a  third  is  taken  up  by  the 
head  alone.  The  oil  is  derived  from  a  thick  layer  of  fat  or 
"blubber,"  which  is  situated  under  the  skin,  and  serves  to  pro- 
tect the  animal  from  cold.  Though  an  inhabitant  of  the  sea,  the 
whale  is  obliged  to  come  to  the  surface  to  breathe,  and  in  so 
doing  it  ejects  from  the  blow-holes  what  looks  like  a  column 
of  water,  the  whole  operation  being  known  to  the  whalers  as 
"  blowing."  The  true  nature  of  this  act  is  still  somewhat 
questionable,  but  it  appears  certain  that  the  apparent  jet  of 
water  is  in  reality,  mainly  if  not  entirely,  due  to  the  condensa- 
tion of  the  moisture  which  is  contained  in  the  air  expelled  from 
the  lungs.  The  old  view  was  that  "  blowing  "  consisted  in 
the  whale  ejecting  through  the  nose  the  water  which  had  pre- 
viously been  filtered  through  the  baleen-plates  of  the  mouth  ; 
but  it  appears  to  be  quite  certain  that  this  view,  at  any  rate, 
is  not  the  correct  one.  The  Rorquals  or  Finner  Whales  re- 
semble the  Greenland  Whale  in  most  respects,  but  the  skin  is 
furrowed  with  deep  plaits  or  folds,  and  there  is  a  dorsal  fin, 
placed  on  the  back.  Some  of  these  attain  a  gigantic  size 
(eighty  feet  or  more),  but  the}'  are  seldom  captured,  as  their 
commercial  value  is  small. 

The  Toothed  Whales  ( Odontoceti)  are  best  known  by  the 
Sperm  Whale,  an  animal  as  large  as,  or  larger  than,  the  Green- 
land Whale,  but  distinguished  by  having  numerous  conical 
teeth,  a  single  blow-hole,  and  a  curiously-truncated  head. 
They  yield  an  excellent  oil,  and  the  singular  fatty  substance 
which  is  known  as  "  spermaceti."  They  also  yield  the  sub- 
stance called  "  ambergris,"  which  is  used  as  a  perfume ;  but 
this  is  probably  a  product  of  disease. 


296  VERTEBRATE  ANIMALS. 

The  last  family  of  the  Cetacea  is  that  of  the  Delphinidce, 
comprising  the  Dolphins  (Fig.  146)  and  Porpoises.  They  have 
numerous  conical  teeth  in  both  jaws,  and  the  nostrils  open  by 
a  single  aperture  on  the  top  of  the  head.  The  Dolphins  are 


FIG.  146.— Cetacea.    The  Common  Dolphin  (DelpMnus  delpTiis). 

inhabitants  of  the  sea,  but  two  species  live  in  rivers — one  in 
India,  and  the  other  in  America.  The  Porpoises  are  also 
marine,  and  occur  in  all  seas.  The  most  remarkable  of  the 
Delphinidce  is  the  Narwhal  or  Sea-Unicorn,  which  is  found  in 
the  Arctic  seas,  and  which  attains  a  length  of  as  much  as  fif- 
teen feet  in  the  body  alone.  The  chief  peculiarity  of  the  Nar- 
whal is  in  the  dentition.  The  females,  as  a  rule,  have  no  teeth, 
the  upper  jaw  alone  having  two  rudimentary  incisors  which 
never  cut  the  gum.  In  the  males,  however,  while  the  lower 
jaw  id  without  teeth,  one  of  the  two  central  incisors  of  the 
upper  jaw  is  enormously  developed,  and  grows  throughout 
the  life  of  the  animal.  It  forms  a  tusk  of  from  eight  to  ten 
feet  in  length,  the  whole  surface  of  which  is  spirally  twisted. 
The  function  of  this  extraordinary  tooth  is  doubtless  offensive. 

ORDER  VI.  UNGULATA  (Lat.  ungula,  a  hoof). — This  order 
is  often  spoken  of  as  that  of  the  Hoofed  Quadrupeds,  and  is 
one  of  the  largest  and  most  important  of  the  orders  of  Mam- 
malia. The  order  is  characterized  by  having  all  the  four  limbs 
and  by  having  that  portion  of  the  toe  which  touches  the 
ground  encased  in  a  greatly-expanded  nail  or  hoof.  There  are 
never  more  than  four  full-sized  toes  to  each  leg,  and  owing  to 
the  presence  of  hoofs  the  limbs  are  useless  for  grasping,  and 
are  only  of  use  in  locomotion  and  in  supporting  the  weight  of 
the  body.  There  are  always  two  sets  of  teeth,  and  the  molars 
have  broad  crowns  adapted  for  grinding  vegetable  sub- 
stances. 

The  Ungulata  are  divided  into  two  great  primary  sections, 
according  as  the  toes  are  even  or  odd  in  number : 


ORDERS   OF  MAMMALIA. 


297 


A..  Perissodactyla,  or  Odd-toed  Ungulates,  in  which  the 
toes  are  odd  in  number — either  one  or  three*  If  horns 
are  present,  they  are  not  in  pairs. 

J3.  Artiodactyla,  or  Even-toed  Ungulates,  in  which  the 
toes  are  even  in  number — either  two  or  four  /  and,  if 
horns  are  present,  they  are  in  pairs. 

The  living  Perissodactyle  Ungulates  are  the  Rhinoceroses, 
the  Tapirs,  and  the  Horse  and  its  allies.  The  Rhinoceroses 
are  extremely  large  and  bulky  brutes,  having  a  very  thick  and 
nearly  hairless  skin,  usually  thrown  into  deep  folds.  The 
feet  (Fig.  147,  D)  are  furnished  with  three  toes  each,  all  en- 


FIG.  147.— Ungulata.    A,  Perissodactyle  foot  of  Zebra.     B,  Artiodactyle  foot  of  Llama. 
C,  Artiodactyle  foot  of  Antelope.     D,  Perissodactyle  foot  of  Ehinoceros. 

cased  in  hoofs.  The  nose  is  furnished  with  one  or  two  horns, 
composed  of  longitudinal  fibres  compacted  together,  and  not 
having  any  central  core  of  bone.  When  there  is  only  one 
horn,  it  is,  of  course,  unsymmetrical ;  and,  when  there  are  two, 
these  are  not  paired,  but  one  is  always  placed  behind  the  other 
in  the  middle  line  of  the  head,  and  the  hinder  one  is  much  the 
shorter.  The  various  species  of  Rhinoceros  are  found  in 
India,  Java,  Sumatra,  and  Africa,  inhabiting  marshy  places 
and  feeding  chiefly  on  the  foliage  of  trees.  The  Tapirs  have 
four  toes  to  each  of  the  fore-legs,  but  only  three  toes  on  the 
hind-legs,  so  that  they  are  properly  odd-toed.  The  nose  forms 
a  short,  movable  proboscis,  used  in  stripping-  off  the  leaves  of 
trees.  They  are  large,  clumsy  animals,  which  inhabit  South 

*  The  fore-feet  of  the  Tapirs  are  even-toed,  but  the  hind-feet  are  perissodactyle. 


298  VERTEBRATE  ANIMALS. 

America,  Sumatra,  and  Malacca.  The  third  and  last  family  of 
the  Perissodaelyla  is  that  of  the  Equidcz,  comprising  the 
Horse,  Ass,  Zebra,  and  Quagga.  In  this  family  the  toes  are 
reduced  to  one  to  each  foot,  enclosed  in  a  single  broad  hoof, 


FIG.  148.—  Head  of  Two-horned  Ehinoceros  (S.  Mcamis). 

without  any  supplementary  hoofs.  There  is  a  continuous 
series  of  incisor  teeth  in  both  jaws,  and  in  the  males  canines 
are  present.  The  dental  formula  is  : 

.3—3         1—1  3—3         3—3 


All  the  varieties  of  Horses  appear  to  be  descended  from 
the  single  species  Equus  cabattus,  which  seems  to  have  been 
primitively  a  native  of  Central  Asia.  When  the  American 
Continent  was  discovered  it  certainly  possessed  no  living  horse, 
but  the  horse  has  now  become  completely  naturalized  there, 
and  we  know  that  America  formerly  possessed  about  twenty 
species  of  horses,  all  of  which  are  now  extinct.  In  the  genus 
A.sinus  are  the  Asses,  Zebras,  and  Quaggas.  The  Wild  Ass 
is  a  native  of  Asia,  and  the  domestic  Ass  is  probably  descended 
from  it.  The  Zebras  and  Quaggas  are  exclusively  African,  and 
are  distinguished  by  their  beautifully-striped  and  banded 
bodies. 

The  Artiodactyles  or  Even-toed  Ungulates  are  divided  into 
two  groups  : 

1.  Omnivora,  as  the  Pig  and  Hippopotamus. 

2.  Ruminantia,  which  chew  the  cud,  such  as  Oxen,  Deer, 
Camels,  etc. 

Of  the    Omnivorous  forms  the   Hippopotamus  or  River- 


OKDERS  OF  MAMMALIA.  299 

horse  is  characterized  by  its  massive  heavy  body,  short  blunt 
muzzle,  and  feet  with  four  hoofed  toes  each.  The  Hippopota- 
mus is  found  in  the  rivers  of  Abyssinia,  and  throughout  the 
whole  of  Africa  to  the  south  of  this.  It  reaches  a  length  of 
from  eleven  to  twelve  feet,  is  nocturnal  in  its  habits,  and  swims 
and  dives  with  great  facility.  It  lives  upon  vegetable  food, 
and  is  tolerably  harmless  unless  attacked  or  irritated.  The 
Pigs,  Peccaries,  and  Wart-hogs,  constitute  the  family  jSuida, 
and  have  usually  four  toes  to  each  foot,  though  sometimes  the 
hind-feet  have  only  three  toes.  All  the  toes  are  hoofed,  but  it 
is  only  two  which  support  the  weight  of  the  body,  the  remain- 
ing toe  or  toes  being  placed  at  some  elevation  on  the  back  of 
the  foot.  The  snout  is  truncated  and  cylindrical,  and  is  ca- 
pable of  extensive  movement.  The  tail  is  very  short,  or  is 
represented  only  by  a  tubercle. 

Of  the  Swine  the  most  important  and  best  known  is  the 
Wild  Boar  (Sus  scrofa],  from  which  it  is  probable  that  all  our 
domestic  varieties  of  swine  have  sprung.  Another  form  is  the 
Babyroussa  or  Hog-deer  (Sus  babyrussa),  which  inhabits  the 
Indian  Archipelago,  and  is  remarkable  for  the  great  size  and 
backward  curvature  of  the  upper  canine  teeth.  The  Wart- 
hogs  (Phacochoerus)  are  African,  and  derive  their  name  from 
the  possession  of  a  fleshy  wart  under  each  eye.  The  Peccaries 
are  exclusively  American,  the  best-known  species  being  the 
Collared  Peccary  (Dicotyles  torquatus).  They  are  not  at  all 
unlike  small  pigs  both  in  appearance  and  habits,  and  they  are 
generally  found  in  small  flocks. 

The  Muminantia  form  a  most  natural  group  of  the  Ungu- 
lata,  characterized  by  the  structure  of  the  foot,  the  dentition, 
and  the  structure  of  the  stomach. 

The  foot  is  "  cloven,"  consisting  of  a  symmetrical  pair  of 
toes,  encased  in  hoofs,  and  looking  as  if  produced  by  the  cleav- 
age of  a  single  hoof.  In  most  cases  there  are  also  two  small 
supplementary  hoofed  toes  placed  on  the  back  of  the  foot. 

As  regards  the  dentition,  the  typical  state  of  things  is  that 
there  should  be  no  incisor  nor  canine  teeth  in  the  upper  jaw, 
but  that  the  lower  jaw  should  have  six  incisors  and  two  canines, 
which  are  all  similar  in  size  and  form,  and  constitute  a  con- 
tinuous and  uninterrupted  series  of  eight  teeth  placed  in  the 
front  of  the  lower  jaw.  There  are  six  molar  teeth  on  each 
side  of  each  jaw,  and  these  have  grinding  surfaces.  The  typi- 
cal dental  formula,  therefore,  for  a  Ruminant  is : 

.0—0         0—0  6—6 


300  VERTEBKATE  ANIMALS. 

In  the  absence  of  incisor  teeth  in  the  upper  jaw,  the  lower 
incisors  bite  against  a  callous  pad  of  hardened  gum.  The 
Camel  tribe  differs  in  its  dentition  from  the  above  typical 
formula,  and  certain  exceptions  likewise  occur  in  the  males 
of  some  other  forms,  and  in  one  or  two  other  less  important 
instances. 

The  stomach  in  the  Ruminants  is  complex,  and  is  divided 
into  several  compartments,  this  being  in  accordance  with  their 
mode  of  eating.  They  all,  namely, "  ruminate  "  or  "  chew  the 
cud ;  "  that  is  to  say,  they  first  swallow  their  food  unmasti- 
cated,  and  then  bring  it  up  again  after  a  longer  or  shorter 
period  in  order  to  chew  it.  This  is  effected  as  follows  (Fig. 
149) :  The  gullet  opens  at  a  point  between  the  first  two  com- 


FIG.  149.— Stomach  of  a  Sheep,    o  Gullet ;  r  Rumen  or  Paunch ;  h  Honeycomb  "bag  or 
Reticulwm  ;  p  Many -plies  or  Psalteriwn  ;  a  Abomasum  or  Fourth  Stomach. 

partments  or  stomachs,  of  which  the  largest  lies  to  the  left  and 
is  called  the  "  paunch,"  while  the  smaller  right  cavity  is  called 
the  "honeycomb  bag"  (reticulum).  The  paunch  (rumen)  is 
the  cavity  into  which  the  food  is  first  received,  and  here  it  is 
moistened  and  allowed  to  soak  for  some  time.  After  the  food 
has  lain  sufficiently  long  in  the  paunch,  it  passes  into  the 
"honeycomb  bag,"  where  it  is  made  up  into  little  balls  or 
pellets,  which  are  then  returned,  to  the  mouth  by  a  reversed 
action  of  the  muscles  of  the  gullet.  After  having  been  thor- 
oughly chewed,  and  prepared  for  digestion,  the  food  is  now 
swallowed  a  second  time.  On  this  occasion,  however,  instead 
of  passing  into  the  paunch,  the  masticated  food  is  conveyed 
into  the  third  stomach.  This  is  known  as  the  "  many-plies 
or  "psalterium"  because  its  lining  membrane  is  thrown  into 
a  number  of  longitudinal  folds,  like  the  leaves  of  a  book.  The 


ORDERS   OF  MAMMALIA.  301 

psalterium  opens  by  a  wide  aperture  into  the  fourth  and  last 
stomach,  known  as  the  "  abomasum"  This  is  a  cavity  of 
considerable  size,  which  secretes  the  true  digestive  fluid  (gas- 
tric juice),  and  it  is  here  that  the  food  is  really  digested.  The 
abomasum  terminates,  of  course,  in  the  commencement  of  the 
small  intestine. 

The  Huminantia  include  a  number  of  families,  of  which  it 
is  only  possible  to  notice  the  leading  characters  of  the  more 
important  ones — namely,  the  Camelidce,  Cervidce,  Giraffes, 
and  Cavieornia. 

The  family  Camelidce  comprises  the  Camel  and  Dromedary 
of  the  Old  World  and  the  Llamas  of  the  New,  and  is  charac- 
terized by  having  no  horns,  by  having  two  incisors  in  the 
upper  jaw,  and  a  pair  of  canines  in  both  jaws  ;  while  the  foot 
consists  of  only  two  toes,  covered  with  imperfect  nail-like 
hoofs,  and  destitute  of  the  two  supplementary  toes.  The  soles 
of  the  feet  are  covered  with  a  callous  horny  integument  upon 
which  the  animal  walks.  In  the  Camels  the  toes  are  conjoined 
below  by  a  callous  pad,  and  the  back  is  furnished  with  one  or 
two  fleshy  humps.  The  Arabian  Camel  or  Dromedary  has  but 
one  hump,  and  its  structure  admirably  adapts  it  for  a  beast  of 
burden  in  the  sandy  deserts  of  Arabia  and  Africa.  One  special 
provision  toward  this  end  is  the  possession  of  large  cells  in 
the  paunch,  in  which  a  large  quantity  of  water  can  be  stored 
up,  thus  enabling  the  animal  to  travel  for  days  without  drink- 
ing. The  Bactrian  Camel  resembles  the  Dromedary  in  most 
respects,  but  it  possesses  two  humps.  The  place  of  the  Camels 
of  the  Old  World  is  filled  in  South  America  by  the  Llamas  and 
Alpacas  (Auchenid),  which  have  separate  toes,  and  have  no 
hump.  The  Llama  is  extensively  used  as  a  beast  of  burden, 
but  the  Alpaca  is  chiefly  of  value  for  its  long  wool,  which  is 
largely  manufactured. 

The  family  Cervidce  includes  the  true  Deer,  and  is  charac- 
terized by  the  fact  that  the  forehead  carries  two  solid  bony 
antlers,  which  are  not  hollow,  and  are  usually  much  branched. 
With  the  single  exception  of  the  Reindeer,  these  appendages 
are  exclusively  confined  to  the  males,  and  they  are  deciduous; 
that  is  to  say,  they  are  only  produced  at  certain  seasons  (an- 
nually, at  the  breeding-season),  and,  when  they  have  fulfilled 
their  purpose,  they  are  shed.  They  increase  in  size  and  in 
the  number  of  branches  every  time  they  are  reproduced,  till  in 
the  old  males  they  may  attain  an  enormous  size.  Among  the 
more  familiar  of  the  Deer  may  be  mentioned  the  Elk,  or  Moose 
(Aloes  Americanus)  of  Scandinavia  and  North  America,  the 


302  VERTEBRATE  ANIMALS. 

Reindeer  and  Caribou  (  Cervus  tarandus)  of  Northern  Europe, 
Asia,  and  North  America ;  the  Red  Deer  ( Cervus  elaphus,  Fig. 
150)  of  Europe ;  the  Wapiti  ( C.  Canadensis)  of  Canada ;  and 
the  Roebuck  ( Capreolus  caproea)  of  Northern  Europe. 


FIG.  150.— Cervidse.— Head  of  Stag  (Cervw  elaphw). 

Of  the  Giraffes  or  Cqmelopardalidce  there  is  only  a  single 
living  species,  exclusively  confined  to  the  African  Continent. 
Both  sexes  have  two  pairs  of  short  horns,  carried  on  the  fore- 
head ;  but  these  are  persistent,  and  are  covered  with  a  hairy 
skin.  The  neck  is  extremely  long,  and  the  fore-legs  much 
longer  than  the  hind-legs.  It  is  the  largest  of  living  Ruminants, 
and  measures  as  much  as  from  fifteen  to  eighteen  feet  in 
height. 

The  Cavicornia  or  Hollow-horned  Ruminants  comprise 
the  Oxen,  Sheep,  Goats,  and  Antelopes,  and  are  characterized 
by  having  horns,  which  may  be  present  in  one  or  both  sexes, 
and  consist  of  a  horny  sheath  surrounding  a  central  bony  axis, 
or  "  horn-core."  The  horns  are  persistent,  and  are  not  peri- 
odically shed,  and  there  is  usually  only  a  single  pair,  though 
sometimes  there  are  two  pairs.  In  their  dentition,  and  in 


ORDERS  OF  MAMMALIA.  303 

other  respects,  the  Cavicornia  are  to  be  regarded  as  being 
the  most  typical  examples  of  the  Ruminantia^  and  they  in- 
clude a  number  of  animals  which  are  of  the  highest  utility  to 
man.  The  Antelopes  form  a  very  extensive  group,  closely  re- 
sembling the  true  Deer,  but  distinguished  by  the  possession 
of  hollow  horns,  in  place  of  solid  antlers.  Most  of  the  Ante- 
lopes are  African,  and  there  are  only  two  European  forms  (the 
Chamois  being  one),  while  America  possesses  only  the  Prong- 
buck  (Antilope  furcifer).  Among  the  more  familiar  African 
species  may  be  mentioned  the  Gazelle,  the  Koodoo  (Fig.  151), 


FIG.  151.— Antelopidae.    Head  of  the  Koodoo  (Strepsiceros  Koodoo}. 

the  Gnu,  the  Gemsbok,  and  the  Springbok.  The  Sheep  and 
the  Goats  (Ovidce)  are  closely  allied  to  one  another,  and  are 
well  known  by  their  domestic  varieties.  All  the  Sheep  appear 
to  be  natives  of  the  Old  World,  with  the  exception  of  the 
"  Bighorn  "  ( Ovis  montana)  of  the  Rocky  Mountains.  Among 
the  true  Oxen  (jBovidce)  the  most  important  species  is  the 
domestic  Ox  (JBos  taunts)  with  its  innumerable  varieties.  The 
true  Buffalos  (Bubalus)  are  natives  of  Asia  and  Africa,  and 
are  characterized  by  their  wide  horns  united  at  the  base.  The 
American  Buffalo,  or  Bison,  as  it  is  properly  called  (JBison 
Americanus},  is  distinguished  by  its  enormous  head,  shaggy 
mane,  and  conical  hump  between  the  shoulders.  America  also 
possesses  another  singular  Ox  in  the  person  of  the  Musk  Ox 
(  Ovibos  moschatus\  which  is  found  north  of  the  60th  parallel, 
and  is  remarkable  for  its  small  size  and  long,  woolly  coat. 

ORDER  VII.    HYRACOIDEA  (Gr.  hurax,  a  shrew;   eictos, 
form). — This  order  includes  only  a  single  small  genus  (Hyrar), 


304  VERTEBRATE  ANIMALS. 

of  which  only  a  few  species  are  known.  They  are  all  gregarious 
little  animals,  living  in  holes  of  the  rocks,  and  capable  of  do- 
mestication. One  species  (Hyrax  Capensis),  occurs  commonly 
in  South  Africa,  and  is  known  to  the  Dutch  colonists  as  the 
"  Badger."  Another  species  (Hyrax  Syriacus)  occurs  in  the 
rocky  parts  of  Arabia  and  Palestine,  and  is  believed  to  be  the 
"  cony  "  of  Scripture.  They  present  many  curious  points  of 
resemblance  to  the  gigantic  Rhinoceros,  and  are  often  placed 
in  the  same  order,  the  similarity  being  especially  great  as  re- 
gards the  form  of  the  molar  teeth.  The  incisor  teeth  of  the 
upper  jaw  are  long  and  curved,  with  sharp  cutting  edges,  and 
they  grow  from  a  permanent  pulp,  thus  resembling  the  teeth 
of  the  genuine  Rodents  (such  as  the  Rabbit  or  Beaver). 

ORDER  VIII.  PROBOSCIDEA  (Lat.  proboscis,  the  snout). — 
This  order  is  only  represented  at  the  present  day  by  the  Ele- 
phant, of  which  there  are  only  two  species  living.  One  of 
these  is  the  African  Elephant,  which  is  distinguished  by  its 
convex  forehead  and  great  napping  ears ;  the  other  is  the  In- 
dian Elephant,  which  has  a  concave  forehead  and  small  ears. 
The  Proboscidea  are  characterized  by  having  the  nose  pro- 
longed into  a  cylindrical  trunk  or  proboscis,  at  the  extremity 
of  which  the  nostrils  are  placed  (Fig.  152,  ri).  The  trunk  is 
extremely  flexible  and  highly  sensitive,  and  terminates  in  a 
finger-like  prehensile  lobe.  There  are  no  canine  teeth;  the 
molars  are  few  in  number,  large,  and  transversely  ridged,  or 
furnished  with  tubercles.  In  the  living  forms  there  are  no 
lower  incisors,  but  the  upper  incisors  are  two  in  number,  grow 
from  a  permanent  pulp,  and  constitute  enormous  tusks  (Fig. 
152,  i).  In  some  of  the  extinct  forms  there  are  two  tusk-like 
lower  incisors,  and  sometimes  both  the  lower  and  upper  in- 
cisors are  developed  into  tusks.  The  feet  are  furnished  with 
five  toes  each,  but  these  are  only  partially  indicated  externally 
by  the  divisions  of  the  hoof.  The  animal  walks  upon  thick 
pads  of  integument,  which  constitute  the  soles  of  the  feet. 
The  Indian  Elephant  inhabits  India  and  the  Indian  Archi- 
pelago and  has  five  hoofs  on  the  fore-feet,  but  only  four  on  the 
hind-feet.  Like  the  Ceylon  Elephant,  which  is  a  mere  variety, 
the  males  alone  possess  well-developed  tusks.  The  African 
Elephant  has  four  hoofs  on  the  fore-feet,  and  only  three  on 
the  hind  feet,  while  it  is  smaller  and  darker  in  color  than  the 
Indian  species.  Both  sexes  also  possess  tusks,  though  those 
of  the  males  are  largest.  All  the  Elephants  feed  upon  vege- 
table matter. 


ORDERS    OF   MAMMALIA. 


305 


v^-' 

NU1.*.*"2 


FIG.  152.— Skull  of  the  Indian  Elephant  (Elepfias  Tndicus).  i  Tusk-liko  upper  Incisors; 
m  Lower  .jaw,  with  grinding  molars,  but  without  incisors;  n  Nostrils,  placed  at  the  ex- 
tremity of  the  proboscis. 

Though  there  are  now  but  two  living  species  of  Elephant, 
there  is  no  doubt  but  that  some  of  the  fossil  forms  have  died 
out  since  the  appearance  of  man  upon  the  globe.  Of  these, 
the  best  known  is  the  Mammoth,  frozen  carcases  of  which 
have  been  found  in  the  icy  wilds  of  Siberia. 

ORDER  IX.  CAROTVORA  (Lat.  caro,  flesh ;  voro,  1  devour). — 
The  ninth  order  of  Mammals  is  that  of  the  Carnivora  or  Beasts 
of  Prey,  comprising  the  Lions,  Tigers,  Wolves,  Dogs,  Cats, 
Hyaenas,  Seals,  Walruses,  etc.  The  Carnivora  are  distin- 
guished by  possessing  two  sets  of  teeth,  which  are  simply 
enamelled,  and  are  always  of  three  kinds,  incisors,  canines,  and 
molars,  differing  from  one  another  in  size  and  shape.  The  in- 
cisor teeth  are  generally  six  in  each  jaw;  the  canines  are  al- 
ways two  in  each  jaw,  and  are  much  longer  and  larger  than 
the  other  teeth.  The  molars  are  mostly  cutting-teeth,  fur- 
nished with  sharp,  uneven  edges,  but  one  or  more  of  the  hinder 
teeth  have  tuberculate  crowns.  The  molars,  too,  graduate 


306 


VERTEBRATE  ANIMALS. 


from  a  cutting  to  a  tuberculate  form  as  the  diet  is  strictly  car- 
nivorous or  becomes  more  or  less  miscellaneous. 

The  dental  formula  differs  considerably  in  different  mem- 
bers of  the  order,  but  subjoined  is  the  dental  formula  of  the 
Cats  (Felidce),  which  are  the  most  typical  examples  of  the 
Garni  vora — 


g;.^« 

o — o         1 — 1 


1—1 


=  30. 


Besides  the  strictly  flesh-eating  dentition  of  the  Carnivo- 
ra, the  order  is  distinguished  by  always  having  the  feet  pro- 
vided with  strong,  curved  claws,  and  the  collar-bones  (clavi- 
cles) are  either  quite  rudimentary,  or  are  altogether  absent. 
The  Carnivora  are  divided  into  the  following  three  sections, 
founded  upon  the  nature  of  the  limbs  : 


A 


FIG.  153, 


-Feet  of  Carnivora  (after  Owen).    A,  Plantigrada,  Foot  of  Bear ;  B,  Pinnl 
grada,  Hind-feet  of  Seal;  C,  Digitigrada,  Foot  of  Lion. 


1.  Pinnigrada  (Fig.  153,  B),  in  which  both  the  fore  and 
hind  legs  are  short,  and  the  feet  form  broad,  webbed,  swim- 
ming-paddles.    The  hind-feet  are  placed  very  far  back,  nearly 
in  a  line  with  the  axis  of  the  body,  and  they  form  with  the 
hinder  end  of  the  body  a  powerful  caudal  fin.     In  this  section 
are  the  Seals  and  Walruses. 

2.  Plantigrada  (Fig.   153,  A),  comprising  the  Bears,  in 
which  the  whole,  or  nearly  the  whole,  of  the  foot  is  applied  to 
the  ground,  so  that  the  animal  walks  upon  the  soles  of  the 
feet. 

3.  Digitigrada  (Fig.  153,  C),  comprising  the  Cats,  Lions, 


ORDERS   OF  MAMMALIA.  30 tf 

Tigers,  Dogs,  etc.,  in  which  the  heel  is  raised  from  the  ground, 
and  the  animal  walks  upon  tiptoe. 

The  Seals  and  Walruses,  forming  the  family  Pinnigrada, 
are  distinguished  from  the  other  Carnivora  by  their  adapta- 
tion to  an  aquatic  mode  of  life.  In  this  respect  they  agree 
with  the  thoroughly  aquatic  Whales  and  Dolphins,  but  they 
difler  from  both  the  Cetacea  and  the  Sirenia,  not  only  in  their 
dentition,  but  also  in  always  having  well-developed  hind-limbs. 
The  Seals  (Fig.  154)  are  characterized  by  having  incisor  teeth 
in  both  jaws,  at  the  same  time  that  the  canine  teeth  are  not 
immoderately  developed.  They  form  a  very  numerous  family, 
of  which  species  are  found  in  most  seas  out  of  the  limits  of 


FIG.  154.— Greenland  Seal  (Phoca  Qroenlandica). 

the  tropics.  They  abound,  however,  especially  in  the  seas  of 
the  Arctic  and  Antarctic  regions.  They  are  largely  captured 
both  for  their  oil  and  for  their  fur.  The  Walrus  or  Morse 
( Trichecus)  is  distinguished  from  the  true  Seals  by  the  fact 
that  in  the  adult  only  two  of  the  upper  incisors  are  present ; 
while  the  upper  canines  are  enormously  developed,  and  form 
two  pointed  tusks — fifteen  inches  or  more  in  length — which  are 
directed  downward  between  the  small  lower  canines,  and  pro- 
ject considerably  below  the  chin.  The  Walrus  is  a  large, 
heavy  animal,  from  ten  to  fifteen  feet  in  length,  which  is  found 
in  flocks  in  the  Arctic  seas,  and  is  hunted  both  for  its  blubber 
and  for  the  ivory  of  the  tusks. 

The  Plantigrade  Carnivora  apply  the  whole  or  the  great- 
er part  of  the  sole  of  the  foot  to  the  ground  in  walking ;  and 


308  VERTEBRATE  ANIMALS. 

this  portion  of  the  foot  is  nearly  or  altogether  destitute  of 
hairs,  except  in  the  White  Bear.  The  most  typical  members 
of  the  Plantigrada  are  the  Bears  ( Ursidce),  of  which  the 
common  Brown  Bear  and  the  White  or  Polar  Bear  are  familiar 
examples.  The  Bears  are  much  less  purely  carnivorous  than 
the  majority  of  the  order,  and,  in  accordance  with  their  om- 
nivorous habits,  the  teeth  do  not  exhibit  the  typical  carnivo- 
rous characters.  The  incisors  and  canines  have  their  usual  car- 
nivorous form,  but  the  pr^emolars  and  molars  are  furnished 
with  broad  tubercular  crowns.  The  claws  are  large,  curved, 
and  strong,  but  are  not  retractile.  The  tongue  is  smooth,  the 
ears  small  and  erect,  the  tail  short,  the  nose  mobile,  and  the 
pupil  circular.  Most  of  the  Bears  are  only  carnivorous,  in  so 
far  that  they  eat  flesh  when  they  can  get  it ;  but  a  great  part 
of  their  food  consists  of  roots,  acorns,  honey,  and  even  insects. 
Nearly  related  to  the  true  Bears  are  the  familiar  Raccoons 
(Procyon)  of  America,  the  Coatis  (JVasua)  of  South  America, 
and  the  Wah  (Ailurus)  of  India. 

The  only  remaining  Plantigrades  of  importance  are  the 
Badgers  (Meles)  of  Europe,  Asia,  and  America,  the  Gluttons 
or  Wolverines  (  Grulo)  of  the  same  continents,  and  the  Honey- 
badgers  (Mellivora)  of  Africa. 

Forming  a  kind  of  transition  between  the  Plantigrada  and 
the  Digitigrada  is  a  group  of  Carnivora  which  comprises  nu- 
merous forms,  such  as  the  Weasels,  Otters,  and  Civets,  which 
apply  part,  but  not  the  whole,  of  the  sole  of  the  foot  to  the 
ground. 

The  Weasels  (Mustelidce)  have  short  legs  and  elongated, 
worm-like  bodies,  with  a  stealthy,  gliding  mode  of  progression. 
Good  examples  are  the  Pole-cat,  the  Mink,  the  Ermine,  and 
the  Sable.  The  two  latter  furnish  the  beautiful  and  valuable 
furs  known  by  their  names.  Here  also  belongs  the  Skunk 
(Mephitis) ,  celebrated  for  its  intensely  disagreeable  odor  when 
alarmed  or  irritated.  The  Otters  are  nearly  allied  to  the 
Weasels,  but  have  webbed  feet  adapted  for  swimming.  The 
great  Sea-otter  yields  a  very  valuable  fur.  The  Civets  and 
Genettes  ( Viverridoe)  all  belong  to  the  Old  World.  The  true 
Civet-cat  inhabits  North  Africa,  and  is  furnished  with  a  pouch 
which  secretes  the  peculiar  fatty  substance  which  is  used  as  a 
perfume  under  the  name  of  "  civet." 

The  typical  group  of  the  Carnivora  is  that  of  the  Digiti- 
(jrada,  comprising  the  three  tribes  of  the  Dogs  (Canidce),  the 
Hysenas  (Hycenidce),  and  the  Cats  (Felidce).  The  family 
Canidce  comprises  the  true  Dogs,  the  Wolves,  the  Foxes,  and 


ORDERS  OF  MAMMALIA.  309 

the  Jackals,  all  characterized  by  their  pointed  muzzles,  smooth 
tongues,  and  non-retractile  claws,  and  by  the  fact  that  the 
fore-feet  have  five  toes,  while  the  hind-feet  have  only  four.  In 
the  Hycenidce,  comprising  the  Hyaenas,  there  are  only  four 
toes  to  all  the  feet,  the  muzzle  is  rounded,  the  tongue  is  rough, 
and  the  hind-legs  are  shorter  than  the  fore-legs.  The  Hyaenas 
are  ill-conditioned,  ferocious  animals,  which  occur  in  Africa, 
Asia  Minor,  Arabia,  and  Persia. 

The  most  highly  carnivorous,  and  therefore  the  most  typi- 
cal, group  of  the  (Jarnivora  is  that  of  the  Cats  or  Felidce, 
comprising  the  Lions,  Tigers,  Leopards,  Panthers,  Cats,  and 
others.  In  all  these  the  animal  walks  lightly  upon  the  tips  of 
the  toes,  and  the  soles  of  the  feet  are  hairy.  The  jaws  are 
short,  and,  owing  to  this  and  to  the  great  size  of  the  muscles 
which  move  the  lower  jaw,  the  head  assumes  a  rounded  form, 
with  a  short  muzzle.  The  molars  and  praemolars  are  fewer  in 
number  than  in  any  other  of  the  Carnivora — hence  the  short- 
ness of  the  jaws ;  and  they  are  all  furnished  with  cutting- 
edges,  except  the  last  molar  in  the  upper  jaw,  which  is  tuber- 
culate.  The  legs  are  nearly  of  equal  length,  and  the  hind-feet 
have  only  four  toes,  while  the  fore-feet  have  five  toes  each. 
All  the  toes  are  furnished  with  strong,  curved,  retractile  claws, 
which,  when  not  in  use,  are  withdrawn  within  sheaths  by  the 
action  of  elastic  ligaments.  The  tongue  is  armed  with  horny 
eminences,  which  render  it  rough  and  prickly,  and  adapt  it  for 
the  office  of  licking  flesh  from  the  bones  of  the  prey.  They 
are  all  extremely  light  upon  their  feet,  and  excessively  muscu- 
lar ;  and  all  have  the  habit  of  seizing  their  prey  by  suddenly 
springing  upon  it.  In  this  section  are  the  Lion  (Fells  leo\  the 
Tiger  (Felis  Tigris),  the  Jaguar  (Felis  onca\  the  Puma  (Felis 
concolor),  the  Leopard  (Felis  leopardus)^  the  Lynxes,  and  the 
true  Cats. 

The  Lions  are  entirely  confined  to  the  Old  World,  inhabit- 
ing Southern  Asia  and  Africa.  The  males  are  maned,  and  the 
tail  is  tufted.  The  Royal  Tiger  is  exclusively  Asiatic,  as  are 
most  of  the  Tiger-cats,  but  some  of  the  latter  are  American. 
The  Spotted  Cats  or  Leopards  are  represented,  among  others, 
by  the  Leopard  and  Cheetah  of  the  Old  World,  and  the  well- 
known  Jaguar  of  the  American  Continent.  The  Puma  is  also 
American,  but  its  color  is  uniform.  The  Lynxes  are  distin- 
guished by  their  tufted  ears,  and  are  found  both  in  the  Eastern 
and  Western  hemispheres. 

ORDER  X.  RODENTIA  (Lat.  rodo,  I  gnaw). — In  this  order 


310 


VERTEBRATE  ANIMALS. 


are  a  number  of  small  animals,  characterized  by  the  absence 
of  canine  teeth,  and  the  possession  of  two  long  curved  incisor 
teeth  in  both  jaws,  which  are  separated  by  a  wide  interval 
from  the  molars  (Fig.  155).  There  are  seldom  more  than  two 


FIG.  155.— A,  Skull  of  the  Beaver  (after  Owen);  B,  Diagram  of  one  of  the  incisor  teeth 
of  a  Eodent,  showing  the  chisel-shaped  point,  a  Enamel;  d  Soft  tooth-substance 
(dentine). 

incisors  in  the  upper  jaw  (sometimes  four),  but  there  are  never 
more  than  two  in  the  lower  jaw.  The  molar  teeth  are  few  in 
number  (rarely  more  than  four  on  each  side  of  each  jaw).  The 
feet  are  usually  furnished  with  five  toes  each. 

The  most  characteristic  point  about  the  Rodents  is  to  be 
found  in  the  structure  of  the  incisor  teeth,  which  are  adapted 
for  continuous  gnawing.  They  grow  from  persistent  pulps, 
and  consequently  continue  growing  as  long  as  the  animal  lives. 


FIG.  156.— Hamster  (Cricetus  vulffaris). 


They  are  large,  long,  and  curved,  and  are  covered  in  front  with 
a  layer  of  hard  enamel,  so  that  the  softer  parts  of  the  tooth 


ORDERS   OF  MAMMALIA.  311 

are  placed  behind  (Fig.  155,  B).  The  result  of  this  is,  that 
as  the  tooth  is  used  in  gnawing,  the  softer  parts  behind  wear 
away  more  rapidly  than  the  hard  enamel  in  front,  and  thus  the 
crown  of  the  tooth  acquires  by  use  a  chisel  shape,  bevelled 
away  behind,  and  the  enamel  forms  a  persistent  cutting-edge. 
The  Rodents  are  almost  all  of  small  size,  and  are  very  prolific. 
They  subsist  principally,  if  not  entirely,  on  vegetable  matters, 
especially  the  harder  parts  of  plants,  such  as  the  bark  and 
roots.  Many  possess  the  power  of  building  very  elaborate 
nests,  and  most  of  them  hybernate  (*.  6.,  remain  torpid  through- 
out the  winter).  They  are  very  generally  distributed  over  the 
whole  world. 

The  order  Rodentia  comprises  a  large  number  of  families, 
of  which  little  more  than  the  names  can  be  mentioned.  The 
most  important  families  of  Rodents  are  the  following :  1.  Le- 
poridoR,  comprising  the  Hares  and  Rabbits.  The  Hares  gen- 
erally occur  in  temperate  regions,  but  some  are  African,  and 
one  species  occurs  in  the  Arctic  regions,  while  the  common 
American  Hare  (Lepus  Americanus)  extends  from  Canada  to 
Mexico.  2.  Gavidce,  comprising  the  Capybaras,  Guinea-pigs, 
etc.  The  Capybara  is  the  largest  of  living  Rodents,  and  is 
not  unlike  a  small  pig.  It  is  a  native  of  South  America, 
and  leads  an  amphibious  life.  Here  also  belong  the  Agoutis 
(Dasyprocta]  of  South  America  and  the  West  Indies,  and  the 
Pacas  of  South  America.  3.  Hystricidce,  comprising  the  Por- 
cupines, and  characterized  by  the  fact  that  the  body  is  covered 
with  longer  or  shorter  spines  or  quills  mixed  with  bristly  hairs. 
Most  of  the  Porcupines  live  in  burrows,  and  are  much  like  the 
Rabbits  in  their  habits,  but  some  are  furnished  with  prehen- 
sile tails,  and  live  in  trees.  4.  Castoridce  or  Beaver  family, 
comprising  the  Beaver,  Musquash,  and  Coypu.  The  Beaver 
has  webbed  feet  and  a  scaly  tail,  and  the  fur  is  an  article  of 
considerable  value.  It  inhabits  both  North  America  and 
Europe.  The  Musquash  resembles  the  Beaver  in  many  re- 
spects, and  is  also  a  native  of  Northern  America;  but  the 
Coypu  is  South  American.  5.  MuriddB^  comprising  the  Mice, 
Rats,  Hamster  (Fig.  156),  Lemmings,  etc.  The  Rats  and 
Mice  are  too  well  known  to  require  more  than  merely  to  be 
mentioned.  6.  Dipodidce,  comprising  the  Jerboas  of  the  Old 
World,  and  the  Jumping  Mice  of  America.  7.  Myoxidce,  com- 
prising the  Dormice,  which  must  not  be  confounded  with  the 
true  Mice  on  the  one  hand,  or  with  the  Shrew-mice  on  the 
other  hand.  8.  Sciuridce,  comprising  the  Squirrels,  Flying 
Squirrels,  and  Marmots.  The  Flying  Squirrels  do  not  really 


312  VERTEBRATE  ANIMALS. 

fly,  but,  like  the  "flying"  Phalangers,  they  take  long  leaps 
from  tree  to  tree  by  means  of  laterally-extended  folds  of  skin. 
The  Marmots,  unlike  the  typical  Squirrels,  are  ground-animals, 
and  live  in  burrows.  An  excellent  example  is  afforded  by  the 
Prairie-dog  (Arctomys  Ludovicianus)  of  North  America. 

ORDER  XI.  CHEIROPTERA  (Gr.  cheir,  hand;  pteron,  wing). 
— This  order  is  undoubtedly  one  of  the  most  natural  and  dis- 


FIG.  157.— Skeleton  of  a  Bat  (Pteropus.)    (After  Owen.) 

tinctly  circumscribed  orders  in  the  whole  class  of  the  Mam- 
malia, comprising  only  the  Bats.  In  many  respects,  however, 
it  might  be  well  to  regard  the  order  as  merely  a  modified 
branch  of  the  Insectivora,  just  as  the  Pinnigrada  are  regard- 
ed as  a  modified  offshoot  of  the  Carnivora.  The  Cheiroptera 
or  Bats  are  essentially  characterized  by  the  fact  that  the  fore- 
limbs  are  much  longer  than  the  hind-limbs,  and  have  several  of 
the  fingers  enormously  elongated.  These  enormously  length- 
ened digits  are  united  by  an  expanded  leathery  membrane  or 
"  patagium,"  which  not  only  stretches  between  the  fingers, 
but  is  also  extended  between  the  fore  and  hind  limbs,  and  is 
attached  to  the  sides  of  the  body  (Fig.  157).  The  patagium 


ORDERS  OF  MAMMALIA.  313 

thus  formed  often  includes  the  tail,  and  is  nearly  or  quite 
naked  or  destitute  of  hairs  on  both  sides.  It  is  used  as  an 
organ  of  true  flight,  and,  in  accordance  with  this,  there  are 
well-developed  collar-bones  (clavicles),  and  the  breastbone  is 
furnished  with  a  ridge  for  the  attachment  of  the  pectoral  mus- 
cles. Of  the  fingers  of  the  hand  at  least  three  are  destitute 
of  nails.  The  mammary  glands  are  placed  upon  the  chest. 
Teeth  of  three  kinds  are  always  present,  and  the  canines  are 
always  well  developed. 

The  Bats  are  all  twilight-loving  or  nocturnal  animals,  and 
they  are  the  only  Mammals  which  possess  the  power  of  true 
flight,  though  several  others  can  make  extended  leaps  from 
tree  to  tree.  The  eyes  are  small,  but  the  ears  are  very  large, 
and  their  sense  of  touch  is  most  acute.  During  the  day  they 
retire  to  caves  or  crevices  in  rocks,  where  they  suspend  them- 
selves by  the  short  thumbs,  which  are  provided  with  claws. 
In  their  flight,  though  they  can  turn  with  great  ease,  they  are 
by  no  means  as  rapid  and  active  as  the  true  Birds.  The  tail 
is  sometimes  very  short,  sometimes  moderately  long,  and  is 
usually  included  in  a  continuation  of  the  "  patagium,"  which 
extends  between  the  hind-legs.  The  body  is  covered  with 
hair,  but  the  patagium  is  usually  nearly  or  quite  hairless. 
Most  of  the  Bats  hybernate. 

The  Cheiroptera  are  conveniently  divided  into  the  two 
sections  of  the  Insectivorous  and  Frugivorous  Bats.  In  the 
first  section  are  all  the  bats  of  temperate  climates,  most  of 
which  are  of  very  small  size,  and  all  of  which  live  upon  in- 
sects. Here  also  belong  the  great  Vampire-bats  (Phyttosto- 
midce)  of  South  America.  In  the  second,  or  fruit-eating  sec- 
tion of  the  Cheiroptera,  are  only  the  Fox-bats  (Pteropidce), 
which  are  especially  characteristic  of  the  Pacific  Archipelago, 
inhabiting  Australia,  Java,  Sumatra,  Borneo,  etc.,  but  occur- 
ring also  in  Asia  and  Africa.  They  are  among  the  largest 
of  the  Bats,  one  species — the  Pteropus  edulis  or  Kalong — at- 
taining a  length  of  from  four  to  five  feet  from  the  tip  of  one 
wing  to  the  tip  of  the  other. 

ORDER  XII.  INSECTIVORA  (Lat.  insectum,  an  insect ;  voro, 
I  devour). — The  twelfth  order  of  Mammals  is  that  of  the  In- 
seetivora,  which  comprises  a  number  of  small  animals,  very 
similar  in  many  respects  to  the  Rodents,  but  wanting  the 
peculiar  incisors  of  that  order,  and  also  being  provided  with 
clavicles.  All  the  three  kinds  of  teeth  are  present,  but  the 
dentition  is  very  various,  and  the  only  common  character  is 


814  VERTEBRATE  ANIMALS. 

that  the  crowns  of  the  molar  teeth  are  furnished  with  small 
pointed  eminences  or  cusps,  adapted  for  crushing  insects.  All 
the  toes  have  claws,  there  are  usually  five  toes  to  each  foot, 
and  most  of  the  Insectivora  are  plantigrade,  that  is  to  say, 
walk  upon  the  soles  of  the  feet.  They  are  all  small,  and  they 
exist  over  the  whole  world,  except  in  Australia  and  South 
America,  where  their  place  is  taken  by  Marsupials,  such  as  the 
Opossums. 

The  Insectivora  are  divided  into  the  three  families  of  the 
Moles  (Talpidce),  the  Shrews  (Soricidoe),  and  the  Hedgehogs 
(Erinaceidce).  The  Moles  (Fig.  158)  are  distinguished  by 


FIG.  158. — Insectivora.    Mole  ( Talpa  Europmd). 

having  the  body  covered  with  hair,  the  feet  short  and  formed 
for  digging,  and  the  toes  furnished  with  strong,  curved  claws. 
There  is  no  external  ear,  and  the  eyes  are  either  extremely 
small,  or  are  completely  concealed  beneath  the  fur.  They  are 
all  nocturnal  burrowing  animals.  The  Star-nosed  Moles  ( Con- 
dylurd)  are  American,  but  their  habits  are  like  those  of  the 
European  Mole  (Talpa  Europcea,  Fig.  158).  The  Golden 
Moles  ( Chrysochloris)  are  African,  and  are  remarkable  for  the 
iridescence  of  their  fur.  The  Shrews  are  very  like  the  true 
Mice  in  external  appearance,  but  they  are  really  widely  dif- 
ferent. The  body  is  covered  with  hair,  the  feet  are  not  adapted 
for  digging,  and  there  are  mostly  external  ears,  while  the  eyes 
are  well  developed.  No  division  of  the  Insectivora  is  more 
abundant  or  more  widely  distributed  than  the  Soricidce,  and 
one  of  the  Shrews  is  probably  the  smallest  of  existing  Mam- 
mals, not  exceeding  two  and  a  half  inches  in  length,  counting 
in  the  tail.  Besides  the  true  Shrews  (Sorex),  this  family  in- 
cludes also  the  Elephant  Shrews  (Macroscelides)  of  Africa, 
and  the  common  Water-mole  (Scalops  aquaticus)  of  North 


ORDERS   OF  MAMMALIA.  315 

America.  The  third  family  includes  only  the  well-known 
Hedgehogs,  which  have  the  power  of  rolling  themselves  into 
a  ball  at  the  approach  of  danger,  and  which  have  the  upper 
surface  of  the  body  covered  with  short  prickly  spines,  forming 
a  protective  armor.  The  common  European  Hedgehog  (Eri- 
naceus  Europceus)  is  the  type  of  the  family,  but  other  species 
occur  in  Africa  and  India.  The  "Tenrecs"  (Centetes)  of 
Madagascar  are  closely  allied  to  the  Hedgehogs,  but  have  no 
power  of  rolling  themselves  up.  The  "  Banxrings  "  ( Tupaia) 
of  the  Indian  Archipelago  have  a  long,  compressed  tail,  and  live 
mostly  in  t»ees. 

Before  passing  on  to  the  next  order,  a  few  words  must  be 
said  about  a  curious  transitional  form,  which  has  been  alter- 
nately placed  in  the  Cheiroptera,  the  Insectivora,  or  the 
Quadrumana,  or  has  been  regarded  as  the  type  of  a  separate 
order.  The  animal  alluded  to  is  the  so-called  Flying  Lemur 
( Galeopithecus  volitans),  of  which  more  than  one  species  is 
known  as  inhabiting  the  Indian  Archipelago.  The  leading 
characteristic  in  this  singular  animal  is  the  possession  of  a  fly- 
ing-membrane, which  extends  as  a  broad  expansion  from  the 
nape  of  the  neck  to  the  arms,  from  the  arms  to  the  hind-legs, 
and  from  the  hind-legs  to  the  tail.  The  fingers  are  not  elon- 
gated, and  do  not  support  a  "  patagium,"  so  that  the  animal 
has  no  power  of  true  flight,  but  can  simply  take  extended 
leaps  from  tree  to  tree.  The  Galeopithecus  lives  chiefly  upon 
small  insects  and  birds,  and  it  should,  probably,  be  regarded 
as  an  aberrant  form  of  the  Insectivora. 

ORDER  XIII.  QUADRTJMANA  (Lat.  quatuor,  four ;  manus, 
hand). — The  thirteenth  order  of  Mammals  is  that  of  the  Quad- 
rumana,  comprising  the  Apes,  Monkeys,  Baboons,  and  Le- 
murs. The  characteristic  of  this  order  is  that  the  innermost 
toe  (great-toe)  of  the  hind-limbs  can  be  opposed  to  the  other 
toes,  so  that  the  hind-feet  become  prehensile  hands.  The  term 
"  opposed  "  simply  implies  that  the  toe  can  be  so  adjusted,  as 
regards  the  extremities  of  the  other  toes,  that  any  object  can 
be  grasped  between  them,  just  as  the  thumb  of  the  human 
hand  can  be  "  opposed  "  to  any  of  the  fingers.  The  fore-feet 
may  be  destitute  of  a  thumb,  but,  when  this  is  present,  it  too 
is  generally  opposable  to  the  other  digits,  so  that  the  animal 
becomes  truly  four-handed  or  "  quadrumanous." 

The  Quadrumana  are  divided  into  three  very  natural  sec- 
tions, separated  from  one  another  both  by  their  anatomical 
characters  and  their  geographical  distribution. 


316  VERTEBRATE  ANIMALS. 

Section  A.  Strepsirhina.  —  Characterized  by  having  the 
nostrils  twisted  or  curved,  and  placed  at  the  end  of  the  nose, 
while  the  second  toe  of  the  hind-feet  is  furnished  with  a  claw. 
The  Quadrumana  of  this  section  are  chiefly  referable  to  Mada- 
gascar as  their  geographical  centre,  but  they  spread  from 
Madagascar  westward  into  Africa,  and  eastward  to  the  Indian 
Archipelago.  In  this  family  are  the  Aye-  Aye  (Cheiromys), 
the  Loris  and  Slow  Lemurs  (Nycticebidoe),  and  the  Lemurs 
(Lemuridce).  The  Aye-  Aye  is  confined  to  Madagascar,  and  is 
not  unlike  a  large  squirrel  in  appearance,  having  a  long  bushy 
tail.  The  incisors  grow  from  permanent  pulps,  like  those  of 
Rodents,  and  there  are  no  canines.  The  Loris  and  Slow  Le- 
murs have  either  no  tail  or  a  rudimentary  one,  and  they  are 
confined  to  Southern  Asia,  and  the  great  islands  of  the  Indian 
Archipelago.  The  true  Lemurs  are  natives  of  Madagascar, 
and  are  often  spoken  of  as  "Madagascar  cats."  They  have  a 
soft,  woolly  fur,  and  a  long  tail,  which  is  prehensile.  The  sec- 
ond toe  of  the  hind-foot  has  a  long  and  pointed  claw. 

Section  J3.  Platyrhina.  —  This  section  includes  those  mon- 
keys in  which  the  nostrils  are  simple,  and  are  placed  far  apart  ; 
the  thumbs  of  the  fore-feet  are  wanting,  or,  if  present,  are  not 
opposable  ;  and  the  tail  is  generally  prehensile.  The  Platy- 
rhine  Monkeys  are  exclusively  confined  to  South  America,  oc- 
curring especially  in  Brazil,  and  they  are  all  adapted  for  a  more 
or  less  purely  arboreal  life.  The  best-known  members  of  this 
section  are  the  Marmosets  (Ifapalidce),  and  the  great  family 
of  the  Gebidce,  comprising  the  Spider-monkeys,  the  Howlers, 
and  others.  The  Howlers  (Mycetes)  are  remarkable  for  having 
a  bony  drum  at  the  summit  of  the  windpipe,  by  which  the 
voice  is  rendered  extraordinarily  resonant,  and  peculiarly  weird 
and  terrifying  to  those  who  hear  it. 

Section  C.  Catarhina.  —  In  this,  the  highest  section  of  the 
Quadrumana,  the  nostrils  are  oblique  and  placed  close  to- 
gether, and  the  thumbs  of  all  the  feet  are  opposable,  so  that 
they  are  truly  "  quadrumanous."  The  dental  formula  agrees 
with  that  of  man  : 

.2—2        1—1  2—2        3—3 


The  incisor  teeth,  however,  are  prominent  and  projecting, 
and  the  canines,  especially  in  the  males,  are  large  and  pointed, 
while  the  teeth  form  an  uneven  series.  The  tail  is  never  pre- 
hensile, and  is  sometimes  absent.  Cheek-pouches  are  often 


ORDERS   OF  MAMMALIA.  317 

present.     In  one  single  instance  (  Colobus)  the  thumbs  of  the 
fore-limbs  are  wanting. 


FIG.  159.— Quadrumana.    Green  Monkey  (Cercocebus  salceus).    (After  Cuvier.) 

With  the  single  exception  of  a  Monkey  which  occurs  on 
the  Rock  of  Gibraltar,  all  the  Catarhine  Monkeys  are  confined 
to  Africa  and  Asia.  The  most  typical  forms  of  the  section  are 
the  Semnopitheci  and  Macaques  of  Asia.  Less  typical  are 
the  Baboons,  which  inhabit  Africa,  and  are  among  the  most  re- 
pulsive of  all  the  Quadrumana.  In  these  the  tail  is  always 
short,  and  often  quite  rudimentary.  The  head  is  large,  and 
the  muzzle  greatly  prolonged,  having  the  nostrils  at  its  ex- 
tremity. More  than  any  other  of  the  Monkeys  they  employ 
the  fore-limbs  in  terrestrial  progression,  running  upon  all  fours 
with  the  greatest  ease. 

The  third  family  of  the  Catarhine  Monkeys  is  that  of  the 
Anthropoid  Apes,  so  called  from  their  making  a  nearer  ap- 
proach to  man  in  anatomical  structure  than  is  the  case  with 
any  other  Mammal.  The  Anthropoid  Apes  are  distinguished 
by  having  no  tail,  nor  cheek-pouches.  The  hind-limbs  are 
short — shorter  than  the  fore-limbs — and  the  animal  can  pro- 
gress in  an  erect  or  semi-erect  posture.  At  the  same  time  the 
hind-feet  are  strictly  prehensile,  since  the  thumbs  are  oppos- 


318 


VERTEBRATE  ANIMALS. 


able  to  the  other  toes.  The  canine  teeth  of  the  males  are 
very  long,  strong,  and  pointed,  but  this  is  not  the  case  in  the 
females. 

In  this  tribe  are  the  Gibbons,  the  Chimpanzee,  the  Orang- 
outang, and  the  Gorilla.  The  Gibbons  form  the  genus  Hylo- 
bates,  and  they  belong  to  Asia,  India,  and  the  Indian  Archi- 
pelago. The  anterior  limbs  in  these  monkeys  are  extremely 
long,  and  the  hands  nearly  or  quite  touch  the  ground  when 
the  animal  stands  erect.  The  Orang-outang  (Simla)  has  no 
cheek-pouches,  and  the  hips  are  covered  with  hair.  The  arms 
are  of  excessive  length,  and  the  hind-legs  very  short.  When 
young,  the  head  of  the  Orang-outang  is  not  very  different  from 
that  of  a  child,  but,  as  the  animal  grows,  the  bones  of  the  face 
gradually  lengthen,  while  the  skull  remains  much  about  the 
same ;  great  bony  ridges  are  developed  for  the  attachment  of 
the  muscles  which  act  upon  the  jaws  ;  the  incisors  project ; 
the  canine  teeth  of  the  males  become  long  and  pointed,  till 
ultimately  the  muzzle  becomes  as  pronounced  and  well  marked 
as  in  the  Carnivorous  animals  (Fig.  160,  A).  The  best-known 


FIG.  160.— A,  Skull  of  the  Orang-outang;  B,  Skull  of  a  European  adult. 


species  of  Orang  is  the  Simla  Satyrus,  which  inhabits  Suma- 
tra, Borneo,  and  the  other  larger  islands  of  the  Indian  Archi- 
pelago; but  there  are  probably  other  species  or  varieties. 
The  Chimpanzee  and  Gorilla  both  belong  to  Africa,  and  form 
the  genus  Troglodytes.  The  Chimpanzee  is  a  native  of  West- 
ern Africa,  and  has  the  arms  much  shorter  proportionately 
than  in  the  Gibbons  and  Orangs.  Still  they  are  much  longer 


ORDERS   OF  MAMMALIA.  319 

than  the  hind-limbs,  and  reach  below  the  knees.  The  hands 
are  naked  to  the  wrist,  and  the  face  is  also  naked  and  much 
wrinkled.  The  Gorilla  is  in  most  respects  like  the  Chimpan- 
zee, but  is  much  larger,  attaining  a  height  of  fully  five  feet. 
It  is  a  native  of  Lower  Guinea  and  Equatorial  Africa,  and  is 
enormously  strong  and  very  ferocious.  It  is  now  generally 
looked  upon  as  the  highest  of  the  Anthropoid  Apes. 

ORDER  XIV.  BIMAXA  (Lat.  bis,  twice  ;  manus,  hand).  — 
In  this  order  stands  Man  alone,  and  little,  therefore,  needs  to 
be  said  on  this  head.  Man  is  distinguished  zoologically  from 
all  other  Mammals  by  his  habitually  erect  posture  and  pro- 
gression upon  two  legs.  The  lower  limbs  are  exclusively  de- 
voted to  progression  and  to  supporting  the  weight  of  the  body. 
The  fore-limbs  are  shorter  than  the  legs,  and  have  nothing  to 
do  with  progression.  The  thumb  can  be  opposed  to  the  other 
fingers,  and  the  hands  are  therefore  prehensile.  The  fingers 
and  toes  are  furnished  with  nails  ;  but  the  innermost  digit  of 
the  foot  (the  great-toe)  is  not  capable  of  being  opposed  to  the 
other  toes,  so  that  the  foot  is  useless  as  a  grasping  organ. 
The  foot  is  broad  and  plantigrade,  the  whole  sole  being  ap- 
plied to  the  ground  in  walking. 

The  teeth  are  thirty  -two  in  number,  and  they  form  a  nearly 
even  and  uninterrupted  series,  without  any  gap  or  interval. 
The  dental  formula  is  : 


The  brain  is  more  largely  developed,  and  more  richly  furnished 
with  large  and  deep  foldings  or  convolutions,  than  is  the  case 
in  any  other  Mammal.  Lastly,  Man  is  the  only  terrestrial 
Mammal  in  which  the  body  is  not  furnished  with  a  general 
covering  of  hair. 

The  purely  anatomical  distinctions  between  Man  and  the 
other  Mammals  are  thus  seen  to  be  not  very  striking,  and  of 
themselves  they  would  hardly  entitle  Man  to  the  position  of 
more  than  a  distinct  order  in  the  class  Mammalia.  When, 
however,  we  take  into  account  the  vast  and  un  surmountable 
mental  differences,  both  intellectual  and  moral,  between  Man 
and  the  highest  of  the  brutes,  and  when  we  reflect  that  this 
mental  difference  must  have  some  physical  correspondence, 
it  becomes  a  question  whether  the  group  IZimana  should 
not  have  the  value  of  a  distinct  sub-kingdom,  while  there* 


320  VERTEBRATE  ANIMALS/ 

can  be  little  hesitation  in  giving  Man   at   least  a   class  to 
himself. 

In  the  words  of  Dr.  Pritchard,  "  the  sentiments,  feelings, 
sympathies,  internal  consciousness,  and  mind,  and  the  habi- 
tudes of  mind  and  action  thence  resulting,  are  the  real  and 
essential  characteristics  of  humanity." 


GLOSSARY. 


AB-DO'MEN  (Lat.  abdo,  I  conceal).  The  posterior  cavity  of  the  body,  contain- 
ing the  intestines  and  others  of  the  viscera.  In  many  Invertebrates  there  ia 
no  separation  of  the  body-cavity  into  thorax  and  abdomen,  and  it  is  only  in 
the  higher  Annulosa  that  a  distinct  abdomen  can  be  said  to  exist. 

AB-ER'RANT  (Lat.  dberro,  I  wander  away).    Departing  from  the  regular  type. 

AB-NOR'MAL  (Lat.  aft,  from  ;  norma,  a  rule).  Irregular ;  deviating  from  the 
ordinary  standard. 

AB-O-MA'SUM.    The  fourth  cavity  of  the  complex  stomach  of  the  Ruminants. 

A-BRANOH'I-ATE  (Gr.  a,  without ;  bragcMa,  gills).  Destitute  of  gills  or  bran- 
chiae. 

A-CA-LE'PHJE  (Gr.  cikalephe,  a  nettle).  Applied  formerly  to  the  Jelly-fishes  or 
Sea-nettles,  and  other  Eadiate  animals,  in  consequence  of  their  power  of 
stinging,  derived  from  the  presence  of  microscopic  cells,  called  "  thread- 
cells,"  in  the  integument. 

A-CAN-THO-CEPH'A-LA  (Gr.  akantfia,  a  thorn  ;  keptiale,  head).  A  class  of  para- 
sitic worms  in  which  the  head  is  armed  with  spines. 

A-OAN-THO-ME-TKI'NA  (Gr.  akantha  /  and  metra,  the  womb).  A  family  of  Pro- 
tozoa, characterized  by  having  radiating  siliceous  spines. 

A-OAN-THO-PTER-YG'-I-I  (Gr.  akantha,  spine ;  pterux,  wing).  A  group  of  bony 
fishes  with  spinous  rays  in  the  front  part  of  the  dorsal  fin. 

A-CAR'I-NA  (Gr.  akari,  a  mite).  A  division  of  the  Arachnida,  of  which  the 
Cheese-mite  is  the  type. 

AC-CRE'TION. 

A-CEPH'A-LOUS  (Gr.  a,  without;  kepTiale,  head;.  Not  possessing  a  distinct 
head. 

A-CE-TAB'U-LA  (Lat.  acetabulum,  a  cup).  The  suckers  with  which  the  cephalic 
processes  of  many  Cephalopoda  (Cuttle-fishes)  are  provided. 

A-CE-TAB'U-LUM.    The  cup-shaped  socket  of  the  hip-joint  in  Vertebrates. 

AO'RI-TA  (Gr.  akritos,  confused).  A  term  sometimes  employed  as  synony- 
mous with  Protozoa,  or  the  lowest  division  of  the  animal  kingdom. 

AO-TI-NOM'ERES  (Gr.  aktin,  a  ray ;  meros,  a  part).  The  lobes  which  are 
mapped  out  on  the  surface  of  the  body  of  the  Ctenopliora,  by  the  cteno- 
phores,  or  comb-like  rows  of  cilia. 

AC-TIN-O-SO'MA  (Gr.  aktin ;  and  soma,  body).  Employed  to  designate  the 
entire  body  of  any  Actinozoon,  whether  this  be  simple  (as  in  the  Sea- 
anemones),  or  composed  of  several  zooids  (as  in  most  Corals). 

AC-TIIT-O-ZO'A  (Gr.  aktin;  and  zoon,  an  animal).  That  division  of  the  Coden- 
terata  of  which  the  Sea-anemones  may  be  taken  as  the  ty^pe. 

AD-EL- AR-THRO-SO'MA-TA  (Gr.  adelos,  nidden;  arikros,  joint;  soma,  body). 
An  order  of  the  Arachnida. 

AD-DUO'TOR. 

A-E'RI-AI,. 

A-GAM'IO  (Gr.  a,  without;  gamos,  marriage).  Applied  to  all  forms  of  repro- 
duction in  which  the  sexes  are  not  directly  concerned. 


322  GLOSSARY. 

AL-LAN-TOID'E-A.  The  group  of  Vertebrata  in  which  the  foetus  is  furnished 
with  an  allantois,  comprising  the  Reptiles,  Birds,  and  Mammals. 

AL-LAN-TOIS'  (Gr.  alias,  a  sausage).  One  of  the  "membranes"  of  the  foetus 
in  certain  Vertebrates. 

AL-VE'O-LI  (Lat.  dim.  ot'alvus,  belly").    Applied  to  the  sockets  of  the  teeth. 

AM-BU-LA'CRA  (Lat.  ambulacrum,  a  place  for  walking).  The  perforated  spaces 
or  "avenues"  through  which  are  protruded  the  tube-feet,  by  means  of 
which  locomotion  is  effected  in  the  EcMnoderrnata. 

AM'BU-LA-TO-BY  (Lat.  ambulo,  I  walk).  Formed  for  walking.  Applied  to  a 
single  limb,  or  to  an  entire  animal. 

A-MET-A-BOL'IC  (Gr.  a,  without ;  tnetabole,  change).  Applied  to  those  insects 
which  do  not  possess  wings  when  perfect,  and  which  do  not,  therefore,  pass 
through  any  marked  metamorphosis. 

AM'NI-ON  (Gr.  amnos,  a  lamb).  One  of  the  foetal  membranes  of  the  higher 
Vertebrates. 

AM-NI-O'TA.  The  group  of  Vertebrata  in  which  the  foetus  is  furnished  with 
an  amnion,  comprising  the  Eeptiles,  Birds,  and  Mammals. 

A-M<E'BA  (Gr.  amoibos,  changing).  A  species  of  Rhizopod,  so  called  from  the 
numerous  changes  of  form  which  it  undergoes. 

A-MOE'BI-FORM.   Resembling  an  Amoeba  in  form. 

A-MOR-PHO-ZO'A  (Gr.  a,  without ;  morphe,  shape ;  zoi'n,  animal).  A  name  some- 
times used  to  designate  the  Sponges. 

A-MOR'PHOUS. 

AM-PHIB'I-A  (Gr.  amphi,  both  ;  bios,  life).  The  Frogs,  Newts,  and  the  like, 
which  have  gills  when  young,  but  can  always  breathe  air  directly  when  adult. 

AM-PHI-COS'LOUS  (Gr.  ampM,  at  both  ends;  icoilos,  hollow).  Applied  to  ver- 
tebrae which  are  concave  at  both  ends. 

AM'PHI-DISCS  (Gr.  ampki,  at  both  ends  ;  diskos,  a  quoit,  or  round  plate).  The 
spicula  which  surround  the  gemmules  of  Spongilla,  and  resemble  two 
toothed  wheels  united  by  an  axle. 

AM-PHI-OX'US  (Gr.  ampM,  at  both  ends ;  oxus,  sharp).  The  Lancelet,  a  little 
fish,  which  alone  constitutes  the  order  PharyngoorancMi. 

AM-PHI-PNEUS'TA  (Gr.  ampM^  both  :  pneo,  I  breathe).  Applied  to  the  "  pe- 
rennibranchiate  "  Amphibians  which  retain  their  gills  through  life. 

AM-PHIP'O-DA  (Gr.  ampM  ;  and  pous,  a  foot).    An  order  of  Crustacea. 

A'NAL  (Lat.  anus,  the  vent).  Connected  with  the  anus,  or  situated  near  the 
anus. 

AN-AL-LAN-TOID'E-A.  The  group  of  Vertebrata  in  which  the  embryo  is  not 
furnished  with  an  allantois. 

A-NAL'O-POUS.    Applied  to  parts  which  perform  the  same  function. 

AN-AM-NI-O'TA.  The  group  of  Vertebrata  in  which  the  embryo  is  destitute  of 
an  amnion. 

AN-ARTH-ROP'O-DA  (Gr.  a,  without ;  arthros,  a  joint ;  pous,  foot).  That  divi- 
sion of  Annulose  animals  in  which  there  are  no  articulated  appendages. 

ANCH-Y-LO'SIS  or  ANK-Y-LO'SIS  (Gr.  ankulos,  crooked).  The  union  of  two 
bones  by  osseous  matter,  so  that  they  become  one  bone,  or  are  immovably 
joined  together. 

AN-DROG'Y-KOUS  (Gr.  aner,  a  man ;  gune,  a  woman).  Synonymous  with  her- 
maphrodite, and  implying  that  the  two  sexes  are  united  in  the  same  indi- 
vidual. 

AN'DRO-PHORES  (Gr.  aner,  a  man ;  and  phero,  I  carry).  Applied  to  medusiform 
gonophores  of  the  Hydrozoa,  which  carry  the  spermatozoa,  and  differ  in 
form  from  those  in  which  the  ova  are  developed. 

AN-NEL'I-DA  (a  Gallicised  form  of  Annulata).  The  Ringed  Worms,  which 
form  one  of  the  divisions  of  the  Anarthropoaa. 

AN'NU-LA-TED.    Composed  of  a  succession  of  rings. 

AN-NF-LOI'DA  (Lat.  annulus,  a  ring;  Gr.  eidos,  form).  The  sub-kingdom 
comprising  the  EcMnoderrnata  and  the  Scoleeida  (=  JEcMnozoa). 

AN-NU-LO'SA  (Lat.  annulus).  The  sub-kingdom  comprising  the  AnartTiropoda 
and  the  Arthropoda  or  Articulata,  in  all  of  which  the  body  is  more  or  less 
evidently  composed  of  a  succession  of  rings. 


GLOSSARY.  323 

AN-O-MO-DON'TI-A  (Gr.  anomos,  irregular ;  odous,  tooth).  An  extinct  order  of 
Keptiles,  often  called  Dicynodontia. 

AN-O-MU'RA  (Gr.  anomos,  irregular ;  oura,  tail).  A  tribe  of  Decapod  Crusta- 
cea, of  which  the  Hermit-crab  is  the  type. 

AN-O-PLU'RA  (Gr.  anoplos,  unarmed ;  oura,  tail).    An  order  of  Apterous  Insects. 

A-NOU'RA  (Gr.  o,  without ;  oura,  tail).  The  order  of  Amphibia  comprising 
the  Frogs  and  Toads,  in  which  the  adult  is  destitute  of  a  tail.  Often  called 
Batrachia. 

AN-TEN'N^E  (Lat.  antenna,  a  yard-arm).  The  jointed  horns  or  feelers  pos- 
sessed by  the  majority  of  the  Articulata. 

AN-TEN'NULES  (dim.  of  antennce).  Applied  to  the  smaller  pair  of  antennae  in 
the  Crustacea. 

AN'THRO-POID. 

AN-TI-BRA'CHI-TJM  (Gr.  anti,  in  front  of;  brachion,  the  arm).  The  fore-arm 
of  the  higher  Vertebrates,  composed  of  the  radius  and  ulna. 

ANT'LERS.  Properly  the  branches  of  the  horns  of  the  Deer  tribe  ( Cervidce), 
but  generally  applied  to  the  entire  horns. 

AN'TLI~A  (Lat.  antlia,  a  pump).  The  spiral  trunk  or  proboscis  with  which 
Butterflies  and  other  Lepidopterous  Insects  suck  up  the  juices  of  flowers. 

APH-A-NIP'TE-RA  (Gr.  aphanos,  inconspicuous  ;  pteron,  a  wing).  An  order  of 
Insects  comprising  the  Fleas. 

AP-LA-CEN-TA  JLI-A.  The  section  of  the  Mammalia,  comprising  the  two  divisions 
of  the  Didelphia,  and  Monodelphia,  in  which  the  young  is  not  furnished 
with  a  placenta. 

AP'O-DA  (Gr.  a,  without  ;podes,  feet).  Applied  to  those  fishes  which  have  no 
ventral  fins.  Also  to  the  footless  Ccedlice  among  the  Amphibia. 

AP'O-DAL.    Devoid  of  feet. 

AP-O-DEM'A-TA  (G^.  apodaio,  I  portion  off).  Applied  to  certain  chitinous 
septa  which  divide  the  tissues  in  Crustacea. 

AP'TE-BA  (Gr.  a,  without;  pteron,  a  wing).  A  division  of  Insects,  which  is 
characterized  by  the  absence  of  wings  in  the  adult  condition. 

AP'TER-OUS.    Devoid  of  wings. 

AP'TER-TX  (Gr.  a,  without ;  pterux,  a  wing).  A  wingless  bird  of  New  Zea- 
land, belonging  to  the  order  Cursores. 

A-QUAT'IC. 

A-QUIF'E-ROUS. 

A-RACH'NI-DA  (Gr.  arachne,  a  spider).  A  class  of  the  Articulata,  comprising 
Spiders,  Scorpions,  and  allied  animals. 

AR-A-NE'I-DA. 

AR-BO-RES'CENT.    Branched  like  a  tree. 

AR-CH.S-OP'TE-RYX  (Gr.  archaios,  ancient ;  pterux,  wing).  The  singular  fossil 
bird  which  alone  constitutes  the  order  of  the  Saururoe. 

ARCH-EN-CEPH'A-LA  (Gr.  archo,  I  overrule;  eglcephalos.  brain).  The  name 
applied  by  Owen  to  his  fourth  and  highest*  group  of  Mammalia,  compris- 
ing Man  alone. 

AR-E-NA'CE-OUS.    Sandy,  or  composed  of  grains  of  sand. 

AR-THROP'O-DA. 

AR-TIC-U-LA'TA  (Lat.  articulus,  a  joint).  A  division  of  the  animal  kingdom, 
comprising  Insects,  Centipedes,  Spiders,  and  Crustaceans,  characterized  by 
the  possession  of  jointed  bodies  or  jointed  limbs.  Tt  e  term  Arthropoda  is 
now  more  usually  employed. 

AR-TI-O-DAC'TY-LA  (Gr.  artios,  even ;  daktulos,  a  finger  or  toe).  A  division 
of  the  hoofed  quadrupeds  (  Ungulata}  in  which  each  foot  has  an  even  num- 
ber of  toes  (two  or  four). 

AS-CID-I-OI'DA  (Gr.  askos,  a  bottle ;  eidos,  a  form).  A  synonym  of  Tunicata,  a 
class  of  Molluscous  animals,  which  have  the  shape,  in  many  cases,  of  a  two- 
necked  bottle. 

A-SEX'U-AL.  Applied  to  modes  of  reproduction  in  which  the  sexes  are  not 
concerned. 

A-SIPH'O-NATE.  Not  possessing  a  respiratory  tube  or  siphon.  (Applied  to  a 
division  of  the  Lameltibrancniate  Molluscs.) 


324  GLOSSARY. 

AS'TER-OID  (Gr.  aster,  a  star ;  and  eidos,  form).    Star-shaped,  or  possessing 

radiating  lobes  or  rays  like  a  star-fish. 
AS-TE-ROID'E-A.     An  order  of  JScTiinodermata,  comprising  the  Star-fishes, 

characterized  by  their  rayed  form. 

A-STOM'A-TOTJS  (Gr.  a,  without;  stoma,  mouth).    Not  possessing  a  mouth. 
AT'LAS  (Gr.  the  god  who  holds  up  the  heavens).   The  first  vertebra  of  the  neck, 

which"  articulates  with  and  supports  the  skull. 
A'TRI-UM  (Lat.  for  a  hall).     Applied  to  the  great  chamber  or  "  cloa'ca,"  into 

which  the  intestine  opens  in  the  Tunicata. 
AU-BEL'LA  (Lat.  aurum,  gold)._  Applied  to  the  chrysalides  of  some  Lepidop- 

tera,  on  account  of  their  exhibiting  a  golden  lustre. 
AU'RI-CLE  (Lat.  dim.  of  auris,  ear).    Applied  to  one  of  the  cavities  of  the 

heart,  by  which  blood  is  driven  into  the  ventricle. 
AU-TOPH'A-GI  (Gr.  autos,  self;  phago,  I  eat).    Applied  to  birds  whose  young 

can  run  about  and  obtain  food  for  themselves  as  soon  as  they  escape  from 

the  egg. 

A'VES  (Lat.  avis,  a  bird).    The  class  of  the  Birds. 
AV-I-CU-LA'RI-TTM  (Lat.  avicula,  dim.  of  avis,  a  bird).     A  singular  appendage, 

often  shaped  like  the  head  of  a  bird,  found  in  many  of  the  Polyzoa. 
Axis  (Gr.  axon,  a  pivot).     The  second  vertebra  of  the  neck,  upon  which  the 

skull  and  atlas  usually  rotate. 
Az'y-eos  (Gr.  a,  without;  zugon,  yoke).    Single ;  without  a  fellow. 

BAC-TE'RI-TTM  (Gr.  bakterion,  a  staff).  A  kind  of  staff-shaped  filament  which 
appears  in  organic  infusions  after  they  have  been  exposed  to  the  air. 

BAL'AN-CERS. 

BA-LAN'I-D^:  (Gr.  balanos.  an  acorn).  A  family  of  sessile  Cirripedes,  com- 
monly called  "  Acorn-shells." 

BA-LEEN'  (Lat.  balcena,  a  whale).  The  horny  plates  which  occupy  the  palate 
of  the  true  or  "  whale-bone  "  Whales. 

BAT'I-DES  (Gr.  batos,  a  bramble).  The  family  of  the  Elasmobranchii,  com- 
prising the  Kays. 

BA-TRA'CHI-A  (Gr.  batrachos,  a  frog).  Often  loosely  applied  to  any  of  the 
Amphibia,  but  sometimes  restricted  to  the  Amphibians  as  a  class,  or  to  the 
single  order  of  the  Anoura. 

BI'FID  (Lat.  bis,  twice ;  findo,  I  cleave).    Cleft  into  two  parts  ;  forked. 

BI-LAT'ER-AL  (Lat.  bis,  twice  ;  latus,  a  side).    Having  two  symmetrical  sides. 

BI-MA'NA  (Lat.  bis,  twice ;  manus,  a  hand).  The  order  of  Mammalia  compris- 
ing Man  alone. 

BIP'E-DAL  (Lat.  bis,  twice ;  pes,  foot).    "Walking  upon  two  legs. 

BI-RA'MOUS  (Lat.  bis,  twice ;  ramus,  a  branch).  Applied  to  a  limb  which  is 
divided  into  two  branches  (e.  g.,  the  limbs  of  Cirripedes). 

BI'VALVE  (Lat.  bis,  twice ;  valvce,  folding-doors).  Composed  of  two  plates  or 
valves ;  applied  to  the  shell  or  the  Lamellibranchiata  and  Erachiopoda,  and 
of  the  carapace  of  certain  Crustacea. 

BLAS-TOID'E-A  (Gr.  blastos,  a  bud ;  and  eidos,  form).  An  extinct  order  of  Echi- 
nodermata,  often  called  Pentremites. 

BRACH-I-OP'O-DA  (Gr.  brachion,  an  arm ;  pous,  the  foot).  A  class  of  the  Mol- 
lu&coida,  often  called  "Lamp-shells/'  characterized  by  possessing  two 
fleshy  arms  continued  from  the  sides  of  the  mouth. 

BRA'CHI-UM  (Gr.  ~brachion,  arm).  Applied  to  the  upper  arm  of  Verte- 
brates. 

BRACH-Y-U'RA  (Gr.  brachus,  short ;  oura,  tail).  A  tribe  of  the  Decapod  Crus- 
taceans with  short  tails  (i.  e.,  the  Crabs). 

BRACTS.     (See  Hydrophyllia.) 

BRAD-Y-POD'I-DJE  (Gr.  bradus,  slow ;  podes,  feet).  The  family  of  Edentata 
comprising  the  Sloths. 

BRANCH'I-A  ^Gr.  bragrchia,  the  gills  of  fishes).  A  respiratory  organ  adapted  to 
breathe  air  dissolved  in  water. 

BRANCH' I-ATE.    Possessing  gills  or  branchiae. 

BRAN-OHIF'E-RA  (Gr.  bragchia,  gills ;  and  phero,  I  carry).    A  division  of  Gas- 


GLOSSARY.  325 

teropodous  Molluscs,  in  which  the  respiration  is  aquatic,  and  the  respi- 
ratory organs  are  mostly  in  the  form  of  distinct  gills. 

BRANCH-I-O-GAS-TE-ROP'O-DA  (=  Branchifera). 

BRAN-CHI-OP'O-DA  (Gr.  bragchia;  and pous,  foot).  A  legion  of  Crustacea,  in 
which  the  gills  are  supported  by  the  feet. 

BRAN-CHI-OS'TE-GAL  (Gr.  bragchia,  gills ;  stego,  I  cover).  Applied  to  a  mem- 
brane and  rays  by  which  the  gills  are  protected  in  many  fishes. 

BREV-I-LIN'GUI-A  (Lat.  brevis,  short ;  lingua,  tongue).  A  division  of  the  La- 
certilia. 

BREV-I-PEN-NA'IM:  (Lat.  brevis,  short ;  penna,  a  wing).  A  group  of  the  Na- 
tatorial Birds. 

BRONCH'I  (Gr.  brogchos,  the  windpipe).  The  branches  of  the  windpipe 
(trachea},  by  which  the  air  is  conveyed  to  the  vesicles  of  the  lung. 

BRU'TA  (Lat.  brutus,  heavy,  stupid).  Often  used  to  designate  the  Mamma- 
lian order  of  the  Edentata. 

BRY-O-ZO'A  (Gr.  bruon,,  moss;  zoon,  animal).  A  synonym  of  Polyzoa,,  a  clasa 
of  the  Moiluscoida. 

BUC'CAL  (Lat.  bucca,  mouth  or  cheeks).    Connected  with  the  mouth. 

BUR' SI-FORM  (Lat.  lursa,  a  purse ;  forma,  shape).  Shaped  like  a  purse ;  sub- 
spherical. 

BYS-SIF'E-ROUS.    Producing  a  byssus. 

BYS'SUS  (Gr.  lussos,  flax).  A  term  applied  to  the  silky  filaments  by  which 
the  Pinna,  the  common  Mussel,  and  certain  other  bivalve  Mollusca,  attach 
themselves 'to  foreign  objects. 

CA-DTJ-CI-BRANCH'I-ATE  ([Lat.  caducus,  falling  off :  Gr.  bragchia,  gills).  Applied 

to  those  Amphibians  in  which  the  gills  fall  off  before  maturity  is  reached. 
CA-DU'COUS.    Applied  to  parts  which  fall  off  or  are  shed  during  the  life  of  the 

animal. 

C^E'CAL  (Lat.  ccecus,  blind).    Terminating  blindly,  or  in  a  closed  extremity. 
C^E'CUM  (Lat.  ccecus).    A  tube  which  terminates  blindly. 
CuEs'pi-rosE  (Lat.  ccespes,  a  turf).    Tufted. 
CAI-NO-ZO'IO.     (See  Kainozoic.) 
CAL'CAR  (Lat.  fora  spur).    Applied  to  the  "spurs"  of  Easorial  Birds;  and 

also  to  the  rudiments  of  the  nind  limbs  in  certain  Snakes. 
CAL-CA'RE-OUS  (Lat.  calx,  lime).     Composed  of  carbonate  of  lime. 
CAL'ICE.    The  little  cup  in  which  the  polype  of  a  coralligenous  Zoophyte 

( Actinozoori)  is  contained. 
CAL-Y-CO-PHOR'I-D^E  (Gr.  Tcalux,  a  cup ;  and  phero,  I  carry).    An  order  of  the 

oceanic  Hydrozoa,  so  called  from  their  possessing  bell-shaped  swimming 

organs  (nechocalyces). 
CA'LYX  (Lat.  calyx,  a  cup).    Applied  to  the  cup-shaped  body  of  Vorticdla 

(Protozoa),  or  of  a  Crinoid  (Echinodermata). 

CAM-PAN-U-LAR'I-D^E  (Lat.  campanula,,  a  little  bell).    An  order  of  Hydroid  Zoo- 
phytes. 
CA-NINE'  (Lat.  canis,  a  dog).     The  eye-tooth  of  Mammals,  or  the  tooth  which 

is  placed  at  or  close  to  the  praemaxillary  suture  in  the  upper  jaw,  and  the 

corresponding  tooth  in  the  lower  jaw. 
CA-PIT'U-LUM  (Lat.  dim.  of  caput,  head).    Applied  to  the  body  of  a  Barnacle 

(Lepadidae),  from  its  being  supported  upon  a  stalk  or  peduncle. 
CAR'A-PACE.     A  protective  shield.    Applied  to  the  upper  shells  of  Crabs, 

Lobsters,  and  many  other  Crustacea  /  also  to  the  case  with  which  certain 

of  the  Infusoria  are  provided.    Also  the  upper  half  of  the  immovable  case 

in  which  the  body  of  a  Chelonian  is  protected. 
CAR-I-NA'IM:  (Lat.  carina,  a  keel).     Applied  by  Huxley  to  all  those  birds  in 

which  the  sternum  is  furnished  with  a  median  ridge  or  keel. 
CAR-NIV'O-RA  (Lat.  caro,  flesh ;  voro,  I  devour).    An  order  of  the  Mammalia. 
CAR-NIV'O-ROUS  (Lat.  caro,  flesh ;  voro,  I  devour).    Feeding  upon  flesh. 
CAR'NOSE  (Lat.  caro).    Fleshy. 
CAB-POPH'A-GA  (Gr.  karpos,  fruit ;  phago,  I  eat).    A  section  of  the  Marsw- 

pialia. 

15 


326  GLOSSARY. 

CAR'PITS  (Gr.  karpos,  the  wrist).  The  small  bones  which  intervene  between 
the  fore-arm  and  the  metacarpus. 

CA-TAR'RHIN-A  (Gr.  kata,  downward;  rhines,  nostrils).  A  group  of  the 
Quadrumana. 

CAU'DAL  (Lat.  caiida,  the  tail).    Belonging  to  the  tail. 

CAV-I-COR'NI-A  (Lat.  caw s,  hollow  ;  cornu,  a  horn).  The  "hollow-horned" 
Euminants,  in  which  the  horn  consists  of  a  central  bony  "  horn-core  "  sur- 
rounded by  a  horny  sheath. 

CEN'TRUM  (Gr.  ke-riiron,  the  point  round  which  a  circle  is  described  by  a  pair 
of  compasses).  The  central  portion  or  "  body  "  of  a  vertebra. 

OE-PHAL'IO  (Gr.  kepliale,  head).    Belonging  to  the  head. 

CEPH-A-LO-BRANCH'I-ATE  (Gr.  keghale  ;  audbragcMa,  gills).  Carrying  gills  upon 
the  head.  Applied  to  a  section  of  the  Annelida,  which,  like  the  Serpula, 
have  tufts  of  external  gills  placed  upon  the  head. 

CEPH-A-LOPH'O-RA  (Gr.  kephale;  and#Am?,  I  carry).  Used  svnonymously  with 
Encephala,  to  designate  those  Motlusca  which  possess  a  distinct  head. 

CEPH-A-LOP'O-DA  (Gr.  kephale /  and  podes,  feet).  A  class  of  the  Mollusca.  com- 
prising the  Cuttle-fishes  and  their  allies,  in  which  there  is  a  series  of  arms 
ranged  round  the  head. 

CEPH-A-LO-THO'RAX  (Gr.  kephale;  and  thorax,  chest).  The  anterior  division 
of  the  body  in  many  Crustacea  and  Arachnida,  which  is  composed  of  the 
coalesced  head  and  chest. 

CERE.    The  naked  space  found  at  the  base  of  the  bill  of  some  birds. 

CER'E-BRAL. 

CER'E-BRTTM. 

CER'VI-CAL  (Gr.  cervix,  neck).    Connected  with  the  region  of  the  neck. 

CES-TOID'E-A  (Gr.  kestos,  a  girdle).  An  old  name  for  the  Twniada,  a  class  of 
intestinal  worms  with  flat  bodies  like  tape  (hence  the  name  Tapeworms). 

CES-TRAPH'O-RI  (Gr.  kestra,  a  weapon ;  phero,  I  carry).  The  group  of  Elasmo- 
branchii  represented  at  the  present  day  by  the  Port  Jackson  Shark. 

CE-TA'CE-A  (Gr.  ketos,  a  whale).  The  order  of  Mammals  comprising  the 
Whales  and  Dolphins. 

CH^-Toa'NA-THA(Gr.  chaite, bristle;  gnathos,ja.v?).  An  order  of  the  Anar- 
thropoda,  comprising  only  the  oceanic  genus  SagiUa. 

CHEI-ROP'TER-A  (Gr.  cheir,  hand ;  pteron,  a  wing).  The  order  of  Mammals 
comprising  the  Bats. 

CHE'LJS  (Gr.  chele,  a  claw).  The  prehensile  claws  with  which  some  of  the 
limbs  are  terminated  in  certain  Crustacea,  such  as  the  Crab,  Lobster,  etc. 

CHE' LATE.    Possessing  chelae ;  applied  to  a  limb. 

CHE-LIO'E-R^:  (Gr.  chele,  a  claw;  and  keras,  a  horn).  The  prehensile  claws 
of  the  Scorpion,  supposed  to  be  homologous  with  antennae. 

CHE-LO'KI-A  (Gr.  chelone,  a  tortoise).  The  order  of  Keptiles  comprising  the 
Tortoises  and  Turtles. 

CHE-LO-NO-BA-TRA'CHI-A  (Gr.  chelone,  a  tortoise ;  batrachos,  a  frog).  Some- 
times applied  to  the  Amphibian  order  of  the  Anoura  (Frogs  and  Toads). 

CHI-LOG'NA-THA  (Gr.  cheilos,  a  lip ;  and  gnathos,  a  jaw).  An  order  of  the  My- 
riapoda. 

CHI-LOP' O-DA  (Gr.  cheilos;  and  podes,  feet).    An  order  of  the  Myriapoda. 

CHI'TINE  (Gr.  cJiiton,  a  coat).  The  peculiar  chemical  principle,  nearly  allied 
to  horn,  which  forms  the  exoskeleton  in  many  Invertebrate  animals,  espe- 
cially in  the  Arthropoda  (Crustacea,  Insecta,  etc.). 

CHLO'RO-PHYLL  (Gr.  chloros,  green ;  and phullon,  a  leaf).  The  green  coloring 
matter  of  plants. 

CHRO-MAT'O-PHORES  (Gr.  chroma,  complexion,  or  color;  and  phero,  I  carry). 
Little  sacs  which  contain  pigment-granules,  and  are  found  in  the  integu- 
ment of  Cuttle-fishes. 

CHRYS'A-LIS  (Gr.  chrusos,  gold).  The  motionless  pupa  of  butterflies  and 
moths,  so  called  because  sometimes  exhibiting  a  golden  lustre. 

CHY-LA'QtJE-ous  FLUID.  A  fluid  consisting  partly  of  water  derived  from  the 
exterior,  and  partly  of  the  products  of  digestion  (chyle),  occupying  the 
body-cavity  or  perivisceral  space  in  many  Invertebrates  (Annelides,  Echino- 


GLOSSARY.  327 

derms,  etc.),  and  sometimes  having  a  special  canal -system  for  its  conduction 
(chylaqueous  canals). 

CHYLE  (Gr.  chulos,  juice).  The  milky  fluid  which  is  the  result  of  the  action 
of  the  various  digestive  fluids  upon  the  food. 

CHY-LIF'IO  (Gr.  chulos,  juice  [chyle] ;  and  Lat.  facio,  I  make).  Producing 
chyle.  Applied  to  one  of  the  stomachs,  when  more  than  one  is  present. 
The  word  is  of  mongrel  origin;  and  " chylopoetic "  is  more  correct. 

CHYME  (Gr.  chumos,  juice).  The  acid,  pasty  fluid  produced  by  the  action  of 
the  gastric  juice  upon  the  food. 

CHYME-MASS.     The  central,  semi-fluid  sarcode  in  the  interior  of  an  Infusorian. 

CIL'I-A  (Lat.  cilium,  an  eyelash).  Microscopic,  hair-like  filaments,  which 
have  the  power  of  lashing  backward  and  forward,  thus  creating  currents  in 
the  surrounding  or  contiguous  fluid,  or  subserving  locomotion  in  the  animal 
which  possesses  them. 

CIL-I-O-GRA'DA  (Lat.  cilium ;  and  gradior,  I  walk).  Synonymous  with  Cteno- 
phora,  an  order  of  Actinozoa. 

CIN'CLI-DES  (Gr.  Icigklis,  a  lattice).  Special  apertures  in  the  column-walls  of 
some  Sea-anemones  (Actinia),  which  probably  serve  for  the  emission  of 
the  cord-like  "  craspeda." 

CIR'RI  (Lat.  cirrus,  a  curl).  Tendril-like  appendages,  such  as  the  feet  of 
Barnacles  and  Acorn-shells  (Cirripedes),  the  lateral  processes  on  the  arms 
of  Bracliiopoda,  etc. 

CIR-RIF'ER-OUS  or  CIR-RIG'ER-OUS.    Carrying  cirri. 

CIR-RI-PE'DIA,  CIR-RHI-PE'DI-A,  or  CIR-RHOP  O-DA  (Lat.  cirrus,  a  curl ;  and^es,  a 
foot).  A  sub-class  of  Crustacea  with  curled  jointed  feet. 

CIR-ROS'TO-MI  (Lat.  cirrus,  a  tendril ;  Gr.  stoma,  mouth).  Sometimes  used  to 
designate  the  Pharyngobranchii. 

CLA-DOC'E-RA  (Gr.  Idados,  &  branch ;  Iceras,  a  horn).  An  order  of  Crustacea 
with  branched  antennae. 

CLA'VATE  (Lat.  clavus}  a  club).     Club-shaped. 

CLAV'I-CLE  (Lat.  clavwula,  a  little  key).  The  "  collar-bone,"  forming  one  of 
the  elements  of  the  pectoral  arch  of  Vertebrates. 

CLO-A'OA  (Lat.  for  a  sink).  The  cavity  into  which  the  intestinal  canal  and 
the  ducts  of  the  generative  and  urinary  organs  open  in  common,  in  some 
Invertebrates  (e.  g.,  in  Insects),  and  also  in  many  Vertebrate  animals. 

CLYP'E-I-FORM  (Lat.  clypeus,  a  shield ;  and  forma,  shape).  Shield-shaped  ; 
applied,  for 'example,  to  the  carapace  of  the  King-crab. 

CNI'D^E  (Gr.  Icnide,  a  nettle).  The  urticating  cells,  or  "  thread-cells,"  where- 
by many  Coelenterate  animals  obtain  their  power  of  stinging. 

COO'CO-LITHS  (Gr.  Tcokkos,  a  berry;  lifhos,  stone).  Minute  oval  or  rounded 
bodies,  which  are  found  either  free  or  attached  to  the  surface  of  coccb- 
spheres. 

Coo' CO-SPHERES  (Gr.  kokkosj  and  sphaira,  a  sphere).  Spherical  masses  of  sar- 
code, enclosed  in  a  delicate  calcareous  envelope,  and  bearing  coccoliths 
upon  their  external  surface.  Both  coccospheres  and  coccoliths  are  em- 
bedded in  a  diffused  plasmodium  of  sarcode,  the  whole  constituting  a  low 
Rhizopodic  organism. 

COC-CYG'E-AL.    Connected  with  the  coccyx. 

COO'CYX  (Gr.  TcoTckux,  a  cuckoo).  The  terminal  portion  of  the  spinal  column 
in  man,  so  called  from  its  resemblance  to  a  cuckoo's  beak. 

CO-COON'  (French  caeon,  the  cocoon  of  the  silk- worm ;  connected  with  Fr. 
cogue,  shell,  which  is  derived  from  the  Lat.  concha}.  The  outer  covering 
ot  silky  hairs  with  which  the  pupa  or  chrysalis  of  many  insects  is  protected. 

CO-DO-NOS'TO-MA  (Gr.  Icodon,  a  bell;  stoma,  mouth).  The  aperture  or  mouth 
of  the  disc  (nechocalyx)  of  a  Medusa,  or  of  the  bell  'gonocalyx)  of  a  medusi- 
form  gonophore. 

C<E-LEN-TE-RA'TA  (Gr.  Icoilos,  hollow;  enieron,  the  bowel).  The  sub-kingdom 
which  comprises  the  Hydrozoa  and  Actinozoa.  Proposed  by  Frey  and 
Leuckhart  in  place  of  the  old  term  Radiata,  which  included  other  animals 
as  well. 

CCB-NEN'CHY-MA  (Gr.  Jcoinos,  common ;  egchuma,  tissue).    The  common  cal- 


328  GLOSSARY. 

careous  tissue  which  unites  together  the  various  corallites  of  a  compound 
corallu7n. 

COE-NOE'CI-UM  (Gr.  koinos,  common ;  oikos,  house).  The  entire  dermal  system 
of  any  Polyzoun  ;  employed  in  place  of  the  terms  polyzOary  or  polypidoin. 

C<EN'O-SARC  (Gr.  koinos,  common ;  sarx,  flesh).  The  common  organized  me- 
dium by  which  the  separate  polypites  of  a  compound  Hydrozoon  are  con- 
nected together. 

COL-E-OP'TER-A  (Gr.  koleos  a  sheath  5  pteron,  wing).  The  order  of  Insects 
(Beetles)  in  which  the  anterior  pair  of  wings  are  hardened,  and  serve  aa 
protective  cases  for  the  posterior  pair  of  membranous  wings. 

COL-U-BRI'NA  (Lat.  coluber,  a  snake).    A  division  of  the  Ophidia. 

COL-UM-BA'CE-I  (Lat.  columba,  a  dove).  The  division  of  Rasorial  Birds  com- 
prising the  Doves  and  Pigeons. 

COL-U-MEL'LA  (Lat.  dim.  of  coluinna,  a  column).  In  Conchology,  the  central 
axis  round  which  the  whorls  of  a  spiral  univalve  are  wound.  Amongst  the 
Actinozoa,  it  is  the  central  axis  or  pillar  which  is  found  in  the  centre  of  the 
thecse  of  many  corals. 

COL'UMN.  Applied  to  the  cylindrical  body  of  a  Sea-anemone  (Actinia) ;  also 
to  the  jointed  stem  or  peduncle  of  the  stalked  Orinoids. 

COM-MIS'SU-RAL  (Lat.  committo,  I  solder  together).  Connecting  together ; 
usually  applied  to  the  nerve-fibres  which  unite  different  ganglia. 

CON'CHA  (Lat.  for  a  shell).  The  external  ear  by  which  sounds  are  collected 
and  transmitted  to  the  internal  ear. 

CON-CHIF'E-RA  (Lat.  concha,  a  shell :  fero,  I  carry).  Shell-fish.  Applied  in  a 
restricted  sense  to  the  bivalve  Molluscs,  and  used  as  a  synonym  for  Lamelli- 
branchiata. 

CON'DYLE  (Gr.  kondulos,  a  knuckle).  The  surface  by  which  one  bone  articu- 
lates with  another.  Applied  especially  to  the  articular  surface  or  sur- 
faces by  which  the  skull  articulates  with  the  vertebral  column. 

CON-I-ROS'TRES  (Lat.  conus,  a  cone ;  rostrum,  a  beak).  The  division  of  Perch- 
ing Birds  with  conical  beaks. 

CO-PEP' O-DA  (Gr.  hope,  an  oar;  podes,  feet).    An  order  of  Crustacea. 

COR'A-COID  (Gr.  Tcorax,  a  crow ;  eidos,  form).  One  of  the  bones  which  enters 
into  the  composition  of  the  pectoral  arch  in  Birds,  Reptiles,  and  Monp- 
tremes.  In  most  Mammals  it  is  a  mere  process  of  the  scapula,  having,  in 
man,  some  resemblance  in  shape  to  the  beak  of  a  crow. 

COR-AL-LIG'EN-OUS.    Producing  a  corallum. 

COR'AL-LITE.  The  corallum  secreted  by  an  Actinozoon  which  consists  of  a 
single  polype :  or  the  portion  of  a  composite  corallum  which  belongs  to, 
And  is  secreteu  by,  an  individual  polype. 

COR-AI/LTJM  (from  the  Latin  for  red  coral).  The  hard  structures  deposited  in, 
or  by.  the  tissues  of  an  Actinozoc.n — commonly  called  a  u  coral." 

CO-RI-A  CEOUS  (Lat.  corium,  hide).    Leathery. 

COR'PUS  CAL-LO'SUM  (Lat.  for  the  "firm  body  ")•  The  great  band  of  nervous 
matter  which  unites  the  two  hemispheres  of  the  cerebrum  in  the  Mammals. 

COR-PUS'CU-LA-TED  (Lat.  corpusculum,  a  little  body  or  particle).  Applied  to 
fluids  which,  like  the  blood,  contain  floating  solid  particles  or  "  corpuscles." 

COR'TI-CAL  LAY'ER.  The  layer  of  consistent  sarcode,  which  in  the  Infusoria 
encloses  the  chyme  mass,  and  is  surrounded  by  the  cuticle.  Sometimes 
called  the  "parenchyma  of  the  body." 

CO-RYN'I-DA. 


outer  surface  of  the  theca,  and  mark  the  position  of  the  septa  within. 
COS'TAL  (Lat.  costa,  a  rib).     Connected  with  the  ribs. 
CBA'NI-UM  (Gr.  kranion,  the  skull).     The  bony  or  cartilaginous  case  in  which 

the  brain  is  contained. 
CRAS'PE-DA  (Gr.  kraspedon,  a  margin  or  fringe).    The  long,  convoluted  cords, 

containing  thread-cells,  which  are  attached  to  the  free  margins  of  the 

mesenteries  of  a  Sea-anemone, 


GLOSSARY.  329 

CRE-PUS'CIJ-LAR  (Lat.  crepusculum,  dusk).  Applied  to  animals  which  are 
active  in  the  dusk  or  twilight. 

CRI-NOI'DE-A  (Gr.  Tcrinon,  a  lily ;  eidos,  form).  An  order  of  EcMnodemnata, 
comprising  forms  which  are  usually  stalked,  and  sometimes  resemble  lilies 
in  shape. 

CROC-O-DIL'IA  (Gr.  krokodeilos,  a  crocodile).     An  order  of  Reptiles. 

CKOP.     A  partial  dilatation  of  the  gullet,  technically  called  "  mgluvies." 

CKUS-TA'CE-A  (Lat.  cru$ta,  a  crust).  A  class  of  articulate  animals,  comprising 
Crabs,  Lobsters,  etc.,  characterized  by  the  possession  of  a  hard  shell  or 
crust,  which  thev  cast  periodically. 

CTEN'O-CYST  (Gr.  «few,  a  comb ;  kustis,  a  bag  or  cyst).  The  sense-organ  (prob- 
ably auditory)  which  occurs  in  the  Ctenophora. 

CTE'NOID  (Gr.  kteis,  a  comb ;  eidos,  form).  Applied  to  those  scales  of  fishes, 
the  hinder  margins  of  which  are  fringed  with  spines  or  comb-like  pro- 
jections. 

CTE-NOPH'O-RA  (Gr.  Icteis,  a  comb ;  andphero,  I  carry).  An  order  of  Actinozoa, 
comprising  oceanic  creatures,  which  swim  by  means  of  "  ctenophores,"  or 
bands  of  cilia  arranged  in  comb-like  plates. 

CUR-SO'KES  (Lat.  curro,  I  run).  An  order  of  Aves,  comprising  birds  destitute 
of  the  power  of  flight,  but  formed  for  running  vigorously  (e.  g.,  the  Ostrich 
and  Emeu). 

CCS'PI-DATE.    Furnished  with  small  pointed  eminences  or  "  cusps." 

CU'TI-CLE  (Lat.  cuticula,  dim.  of  cutis,  skin).  The  pellicle  which  forms  the 
outer  layer  of  the  body  among  the  Infusoria.  The  outer  layer  of  the  in- 
tegument generally. 

CU'TIS  (Lat.  for  skin).  The  inferior  vascular  layer  of  the  integument,  often 
called  the  cutis  vera,  the  corium,  or  the  derma. 

CY'CLOID  (Gr.  kuklos.  a  circle ;  eidos,  form).  Applied  to  those  scales  of  fishes 
which  have  a  regularly  circular  or  elliptical  outline  with  an  even  margin. 

CY-CLOS'TO-MI.  Sometimes  used  to  designate  the  Hag-fishes  and  Lampreys, 
forming  the  order  MarsipobrancTiii. 

CYST  (Gr.  kustis,  a  bladder  or  bag).    A  sac  or  vesicle. 

CYS'TIC. 

CYS'TI-CA.  The  embryonic  forms  (scolices)  of  certain  intestinal  worms  (Tape- 
worms), which  were  described  as  a  distinct  order,  until  their  true  nature 
was  discovered. 

CYS-TOI'DE-A  (Gr.  kustis,  a  bladder ;  and  eidos,  form).  An  extinct  order  of 
JSchinodermata. 

DE-CAP'O-DA  (Gr.  deJca,  ten ;  podes,  feet).    The  division  of  Crustacea  which 

have  ten  ambulatory  feet;  also  the  family  of  Cuttle-fishes,  in  which  there 

are  ten  arms  or  cephalic  processes. 
DE-CID'U-OUS  (Lat.  decido,  I  fall  off).    Applied  to  parts  which  fall  oif  or  are 

shed  during  the  life  of  the  animal. 
DE-COL' LA-TED  (Lat.  decollo,  I  behead).    Applied  to  univalve  shells,  the  apex 

of  which  falls  off  in  the  course  of  growth. 
DEI-NO-SAU'RI-A  (Gr.  deinos,  terrible ;  saura,  lizard).     An  extinct  order  of 

Eeptiles. 
DEN'DRI-FORM:,  DEN-DRIT'IC,  DEN'DROID  (Gr.  dendron,  a  tree).    Branched  like 

a  tree,  arborescent. 
DEN'TAL. 
DEN-TI-ROS'TRES  (Lat.  dens,  a  tooth ;  rostrum,  a  beak).    The  group  of  Perching 

Birds  in  which  the  upper  mandible  of  the  beak  has  its  lower  margin  toothed. 
DER'MA.     (See  Cutis.) 

DER'MAL  (Gr.  derma,  skin).    Belonging  to  the  integument. 
DER-MO-SCLE'RITES  (Gr.  derma,  skin ;  skleros,  hard).    Masses  of  spicules  which 

occur  in  the  tissues  of  some  of  the  Alcyonidce  (Actinozoa). _ 
DES-MID'!-^.    Minute  fresh- water  pi  ints,  of  a  green  color,  without  a  siliceous 

epidermis. 
DEU-TER-O-ZO'OIDS  (Gr.  deuteros,  second;  zocn,  animal;  eidos,  form).     The 

zooids  which  are  produced  by  gemmation  from  zooids. 


330  GLOSSARY. 

DEX'TRAL  (Lat.  dextra,  the  right  hand).  Eight-handed :  applied  to  the  direc- 
tion of  the  spiral  in  the  greater  number  ol  univalve  shells. 

DI'A-PHRAGM  (Gr.  diaphragma,  a  partition).  The  "midriff,"  or  the  muscle 
which  in  Mammalia  forms  a  partition  between  the  cavities  of  the  thorax 
and  abdomen. 

DI-A-STE'MA  (Gr.  dia,  apart;  Tiistemi,  to  place).  A  gap  or  interval,  especially 
between  teeth. 

DI-AS'TO-LE  (Gr.  diastello,  I  separate  or  expand).  The  expansion  of  a  contrac- 
tile cavity  such  as  the  heart,  which  follows  its  contraction  or  "systole." 

DI-A-TO-MA'CE-JE  (Gr.  diatemno,  I  sever).  An  order  of  minute  plants,  which 
are  provided  with  siliceous  envelopes. 

DI-BRAXCH-I-A'TA  (Gr.  dis,  twice;  bragchia.  gills).  The  order  of  Cephalopoda, 
(comprising  the  Cuttle-fishes,  etc.),  in  winch  only  two  gills  are  present. 

DI-OYK-O-DON'TI-A  (Gr.  dis,  twice ;  kuon,  dog ;  odous,  tooth).  An  extinct  order 
of  Keptiles. 

DI-DEL'PHI-A  (Gr.  dis,  twice ;  delphus,  womb).  The  subdivision  of  Mammals 
comprising  the  Marsupials. 

DIG'IT  (Lat.  digitus,  a  finger).    A  finger  or  toe. 

DIG-I-TI-GRA'DA  (Lat.  digitus;  gradior,  I  walk).  A  subdivision  of  the  Car- 
nivora, 

DIG'I-TI  GRADE.  Walking  upon  the  tips  of  the  toes,  and  not  upon  the  soles 
of  the  feet. 

DIM-E-RO-SO'MA-TA (Gr.  dis ;  meros,  part;  soma, body).  A.n  order  of  Arachnida, 
comprising  the  true  Spiders,  so  called  from  the  marked  division  of  the  body 
into  two  regions,  the  cephalothorax  and  abdomen.  The  name  Araneida  is 
often  employed  for  the  order. 

DIM'Y-A-RY  ( Gr.  du,  twice ;  mus,  muscle).  Applied  to  those  bivalve  Molluscs 
(LamellibrancMata)  in  which  the  shell  is  closed  by  two  adductor  muscles. 

DI-CE'OIOUS  (Gr.  dis,  twice ;  oikos.  house).  Having  the  sexes  distinct;  applied 
to  species  which  consist  of  male  and  female  individuals. 

DIPH'Y-O-DONT  (Gr.  dis.  twice;  phuo,  I  generate;  odous,  tooth).  Applied  to 
those  Mammals  which  have  two  sets  of  teeth. 

DIPH-Y-O-ZO'OIDS.  Detached  reproductive  portions  of  adult  Calycophorida,  an 
order  of  oceanic  Hydroaoa. 

DIP'NOI  (Gr.  dis,  twice;  pnoe,  breath).  The  order  of  Fishes  represented  by 
the  Lepidosiren. 

DIP'TER-A  (Gr.  dis,  twice ;  pteron,  wing).  An  order  of  Insects  characterized 
by  the  possession  of  two  wings. 

DISC'OID  (Gr.  diskos,  a  quoit ;  eidos,  form).     Shaped  like  a  round  plate  or  quoit. 

DIS-COPH'O-RA  (Gr.  diskos,  a  quoit ;  phero,  I  carry).  This  term  is  applied  to 
the  Medusae,  or  Jelly-fishes,  from  their  form ;  and  is  sometimes  used  to 
designate  the  order  of  the  Leeches  (Hirudinea),  from  the  suctorial  discs 
which  these  animals  possess. 

DIS-SEP'I-MENTS  (Lat.  dissepio,  I  partition  off).  Partitions.  Used  in  a  restricted 
sense  to  designate  certain  imperfect  transverse  partitions,  which  grow  from 
the  septa  of  many  corals. 

DIS'TAL.  Applied  to  the  quickly-growing  end  of  the  hydrosoma  of  a  Hydro- 
zoon ;  the  opposite,  or  "proximal,"  extremity  growing  less  rapidly,  and 
being  the  end  by  which  the  organism  is  fixed,  when  attached  at  all. 

DI-UR'NAL  (Lat.  dies,  day;.  Applied  to  animals  which  are  active  during  the 
day. 

DI-VER-TIO'U-LUM  (Lat.  diverticulum,  a  by-road).  A  lateral  tube  with  a  blind 
extremity  springing  from  the  side  of  another  tube. 

DOR'SAL  (Lat.  dorsum,  back).     Connected  with  the  back. 

DOR-SI-BRANCH'I-ATE  (Lat.  dorsum,  the  back ;  Gr.  bragckia,  gills).  Having  ex- 
ternal gills  attached  to  the  back ;  applied  to  certain  Annetides  and  Molluscs. 
The  term  is  of  mongrel  composition,  and  "  notobranchiate "  is  more  cor- 
rectly employed. 

EO'DE-ROH  (Gr.  ek,  out:  deros,  skin).  The  outer  plane  of  growth  of  the  ex- 
ternal integumentary  layer  (.viz.,  the  ectoderm,  or  epidermis). 


GLOSSARY.  331 

EC'DY-SIS  (Gr.  ekdusis.  a  stripping  off).    A  shedding  or  moulting  of  the  skin. 

E-CHI-NO-COC'CI  (Gr.  echinos,  a  hedgehog ;  kokkos,&  berry).  The  larval  forms 
(scolices)  of  the  tapeworm  of  the  dog  (Tania  echinococcus),  commonly 
known  as  "  hydatids." 

E-CHI-NO-DER'MA-TA  (Gr.  echinos  ;  and  derma,  skin).  A  class  of  animals  com- 
prising the  Sea-urchins,  Star-fishes,  and  others,  most  of  which  have  spiny 
skins. 

E-CHI-NOI'DE-A  (Gr.  echinos ;  and  eidos,  form).  An  order  of  Echinodermata, 
comprising  the  Sea-urchins. 

E-CHIN'U-LATE.    Possessing  spines. 

EC'TO-CYST  (Gr.  ektos,  outside ;  kustis,  a  bladder).  The  external  investment 
of  the  coenoecium  of  a  Polyzocn. 

EC'TO-DERM  (Gr.  ektos  /  and  derma,  skin).  The  external  integumentary  layer 
of  the  Coelenterata. 

EC'TO-SARC  (Gr.  ektos;  sarx,  flesh).  The  outer  transparent  sarcode-layer  of 
certain  Rhizopods,  such  as  the  Amoeba. 

E-DEN-TA'TA  (Lat.  e,  without ;  dens,  tooth).  An  order  of  Mammalia  often 
called  Bruta. 

E-DEN'TU-LOUS.  Toothless ;  without  any  dental  apparatus.  Applied  to  the 
mouth  of  any  animal,  or  to  the  hinge  of  the  bivalve  Molluscs. 

E-DRI-OPH-THAI/MA-TA  (Gr.  hedraios,  sitting ;  ophthalmos,  eye).  The  division  of 
Crustacea  in  which  the  eyes  are  sessile,  and  are  not  supported  upon 
stalks. 

E-LAS-MO-BRANCH'I-I  (Gr.  elasma,  a  plate ;  bragchia,  gills).  An  order  of 
Fishes,  including  the  Sharks  and  Rays. 

EL'Y-TRA  (Gr.  elutron,  a  sheath).  The  chitinous  anterior  pair  of  wings  in 
Beetles,  which  form  cases  for  the  posterior  membranous  wings.  Also  ap- 
plied to  the  scales  or  plates  on  the  back  of  the  Sea-mouse  (Aphrodite'). 

EM'BRY-O  (Gr.  en,  in;  oruo,  I  swell).  The  earliest  stage  at  wnich  the  young 
animal  is  recognizable  in  the  impregnated  ovum. 

EN-CEPH'A-LON  (Gr.  egkephalos,  brain).  The  portion  of  the  cerebro-spinal 
nervous  axis  contained  within  the  cranium. 

EN-CEPH'A-LOUS  (Gr.  en,  in ;  kephale,  the  head).  Possessing  a  distinct  head. 
Usually  applied  to  all  the  Mollusca  proper,  except  the  Lamellibranchiata. 

EN-CYS-TA'TION  (Gr.  en,  in ;  kustis,  a  bag).  The  transformation  undergone  by 
certain  of  the  Protozoa,  when  they  become  motionless,  and  surround  them- 
selves by  a  thick  coating  or  cyst. 

EN'DE-RON  (Gr.  en,  in ;  deros,  skin).  The  inner  plane  of  growth  of  the  outer 
integumentary  layer  (viz.,  the  ectoderm,  or  epidermis). 

EN'DO-CYST  (Gr.  endon.  within ;  Icustis,  a  bag).  The  inner  membrane  or  in- 
tegumentary layer  or  a  Polyzoon.  In  Crutatella,  where  there  is  no  "  ecto- 
cyst,"  the  endocyst  constitutes  the  entire  integument. 

EN  DO-DERM  (Gr.  endon  ;  and  derma,  skin).  The  inner  integumentary  layer 
of  the  Ccelenterata. 

EN-DOP'O-DITE  (Gr.  endon  ;  andpous,  foot).  The  inner  of  the  two  secondary 
joints  into  which  the  typical  limb  of  a  Crustacean  is  divided. 

EN'DO-SARC  (Gr.  endon;  and  sarx,  flesh).  The  inner  molecular  layer  of  sarcode 
in  the  Amoeba  and  other  allied  Rhizopods. 

EN-DO -SKEL'E-TON  (Gr.  endon;  and  skeletos,  dry).  The  internal  hard  struc- 
tures, such  as  bones,  which  serve  for  the  attachment  of  muscles,  or  the  pro- 
tection of  organs,  and  which  are  not  a  mere  hardening  of  the  integument. 

EN'SI-FORM  (Lat.  ensis,  a  sword;  forma,  shape).    Sword- shaped. 

EN-TO-MOPH  A-GA  (Gr.  entoma,  insects ;  phago,  I  eat).  A  section  of  the  Mar- 
supialia. 

EN-TO-MOS'TRA-KA  (Gr.  entoma,  insects ;  ostrakon,  a  shell).  Literally,  shelled 
insects — applied  to  a  division  of  Crustacea. 

EN-TO-ZO'A  (Gr.  entos,  within ;  zoon,  animal).  Animals  which  are  parasitic  in 
the  interior  of  other  animals. 

E'O-CENB  (Gr.  eos,  dawn ;  kainos,  new  or  recent).  The  lowest  division  of  the 
Tertiary  rocks,  in  which  species  of  existing  shells  are  to  a  small  extent 
represented. 


332  GLOSSARY. 

EP-I-DER'MIS  (Gr.  epi,  upon ;  derma,  the  true  skin).    The  outer  non-vascular 

layer  of  the  skin,  often  called  the  scarf-skin  or  cuticle. 
EP-I-ME'KA  (Gr.  epi,  upon ;  meron,  thigh).     The  lateral  pieces  of  the  dorsal 

arc  of  the  somite  of  a  Crustacean. 
EP-I-PO'DI-A  (Gr.  epi,  upon;  pous,  the  foot).    Muscular  lobes  developed  from 

the  lateral  and  upper  surfaces  of  the  "foot"  of  some  Molluscs. 
E-PIP'O-DITE  (Gr.  epi,  upon ;  pous,  foot).     A  process  developed  upon  the  basal 

joint,  or  "  protopodite,"  of  some  of  the  limbs  of  certain  Crustacea. 
EP-I-STER'NA  (Gr.  epi,  upon ;  sternon,  the  breast-bone).     The  lateral  pieces 

of  the  inferior  or  ventral  arc  of  the  somite  of  a  Crustacean. 
EP'I-STOME  (Gr.  epi;  and  stoma,  mouth).    A  valve-like  organ  which  arches 

over  the  mouth  in  certain  of  the  Polyzoa. 
EP-I-THE'CA  £Gr.  epi  f  and  iheke,  a  sheath).     A  continuous  layer  surrounding 

the  thecse  in  some  Corals,  and  being  the  external  indications  of  tabulae. 
EP-I-ZO'A  (Gr.  epi,  upon;  zoon,  animal).    Animals  which  are  parasitic  upon 

other  animals.     In  a  restricted  sense,  a  division  of  Crustacea  which  are 

parasitic  upon  fishes. 
E-QUI-LAT'ER-AL  (Lat.  cequus,  equal;  latus,  side).     Having  its  sides  equal. 

Usually  applied  to  the  shells  of  the  Brachiopoda.    When  applied  to  the 

spiral  shells  of  the  Foraminifera,  it  means  that  all  the  convolutions  of  the 

shell  lie  in  the  same  plane. 
E'QUI-VALVE  (Lat.  cequus,  equal;  valvce,  folding-doors).     Applied  to  shells 

which  are  composed  of  two  equal  pieces  or  valves. 
ER-RAN'TI-A  (Lat.  erro,  I  wander) .   An  order  of  Annelida,  often  called  Nereidea, 

distinguished  by  their  great  locomotive  powers. 
EU-RYP-TER'I-DA  (Gr.  eurus,  broad ;  pteron,  wing).     An  extinct  sub-order  of 

Crustacea. 
Ex-pp'o-DiTE  (Gr.  exo,  outside ;  pous,  foot).    The  outer  of  the  two  secondary 

joints  into  which  the  typical  limb  of  a  Crustacean  is  divided. 
EX-O-SKEL'E-TON  (Gr.  exo,  outside;   skeletos,  dry).     The  external  skeleton. 

which  is  constituted  by  a  hardening  of  the  integument,  and  is  often  called 

a  u  dermoskeleton." 

FAS-CIC'C-LA-TED  (Lat.  fasciculus,  a  bundle).    Arranged  in  bundles. 

FAU'NA  (Lat.  Fauni,  the  rural  deities  of  the  Romans).  The  general  assem- 
blage of  the  animals  of  any  region  or  district. 

FE'MUR.  The  thigh-bone,  intervening  between  the  pelvis  and  the  bones  of 
the  leg  proper  (tibia  and  fibula). 

FIB'U-LA  (Lat.  a  brooch).  The  outermost  of  the  two  bones  of  the  leg  in  the 
higher  Vertebrata  /  corresponding  to  the  ulna  of  the  fore-arm. 

FIL'I-FORM  (Li&t.filum,  a  thread ;  forma,  shape).    Thread-shaped. 

FIS-SI-LJN'GUI-A  (Lat.  findo,  I  cleave ;  lingua,  tongue).  A  division  of  Lacer- 
tilia,  with  bifid  tongues. 

FIS'SION-  (Lat.  findo,  I  cleave).  Multiplication  by  means  of  a  process  of  self- 
division. 

FIS-SIP'A-ROUS  (Lat.  findo ;  and  pario,  I  produce).  Giving  origin  to  fresh 
structures  by  a  process  of  fission. 

FIS-SI-ROS'TRES  (Lat.  findo,  I  cleave ;  rostrum,  beak).  A  sub-order  of  the 
Perching  Birds. 

FLA-GEL'LUM  (Lat.  for  whip).  The  lash-like  appendage  exhibited  by  many 
Infusoria,  which  are  therefore  said  to  be  "flagellate." 

FLO'RA  (Lat.  Flora}  the  goddess  of  flowers).  The  general  assemblage  of  the 
plants  of  any  region  or  district. 

FOOT. 

FOOT-JAWS.  The  limbs  of  Crustacea,  which  are  modified  to  subserve  mastica- 
tion. 

FOOT-SE-CRE'TION.  The  term  applied  by  Mr.  Dana  to  the  sclerobasic  corallum 
of  certain  Actinozoa. 

FOOT-TU'BER-CLES.  The  unarticulated  appendages  of  the  Annelida,  often 
called  parapodia. 

FO-EAM-I-NIF  K-RA  (Lat.  foramen,  an  aperture ;  fero,  I  carry).    An  order  of 


GLOSSARY.  333 

Protozoa,  usually  characterized  by  the  possession  of  a  shell  perforated  by 

numerous  pseudopodial  apertures. 

FRU-GIV'O-ROUS  (Lat.  frux,  fruit ;  voro,  I  devour).    Living  upon  fruits. 
FUN'NEL. 
FUR'OU-LUM  (Lat.  dim.  of  f  urea,  a  fork).    The  "  merry-thought"  of  birds,  or 

the  V-shaped  bone  formed  by  the  united  clavicles. 
FU'SI-FORM  (Lat.  fusus,  a  spindle ;  and  forma,  shape).    Spindle-shaped,  or 

pointed  at  both  ends. 

GAL-LI-NA'CE-I  (Lat.  gallina,  a  fowl).    Sometimes  applied  to  the  whole  order 

of  the  Kasorial  Birds,  but  properly  restricted  to  that  section  of  the  order 

of  which  the  common  Fowl  is  a  typical  example. 
GAN'GLI-OI*  (Gr.  gagglion,  a  knot).    A  mass  of  nervous  matter  containing 

nerve-cells,  giving  origin  to  nerve-fibres. 
GA'NOID  (Gr.  ganos,  splendor?  brightness).     Applied  to  those  scales  or  plates 

which  are  composed  of  an  inferior  layer  of  true  bone  covered  by  a  superior 

layer  of  polished  enamel. 
GA-NOI'DE-A.    An  order  of  Fishes. 
GAS-TE-ROP'O-DA  (Gr.  gaster,  stomach  ;  pous,  foot).     The  class  of  the  Mollusca 

comprising  the  ordinary  univalves,  in  which  locomotion  is  usually  effected 

by  a  muscular  expansion  of  the  under  surface  of  the  body  (the  "  foot"). 
GEM'M^E  (Lat.  gemma,  a  bud).    The  buds  produced  by  any  animal,  whether 

detached  or  not. 

GEJC-MA'TION!    The  process  of  producing  new  structures  by  budding. 
GEM-MIP'AR-OUS  (Lat.  gemma,  a  bud  ',pario,  I  produce).     Giving  origin  to  new 

structures  by  a  process  of  budding. 
GEM'MULES  (Lat.  dim.  of  gemma).    The  ciliated  embryos  of  many  Cxlenterata  ; 

also  the  seed-like  reproductive  bodies  or  u  spores"  of  Spongilla. 
GE-PHYR'E-A  (Gr.  gephura,  a  bridge).     A  class  of  the  Anarthropoda,  com- 
prising the  Spoon-worms  (Sipunculus}  and  their  allies. 
GIZ'ZARD.    A  muscular  division  of  the  stomach  in  Birds,  Insects,  etc. 
GLA'DI-US  (Lat.  for  a  sword).    Applied  to  the  horny  endoskeleton  or  "pen" 

of  certain  Cuttle-fishes. 

GLE'NOID  (Gr.  glene,  a  cavity ;  eidos,  form).     A  shallow  cavity ;  applied  espe- 
cially to  the  shallow  articular  cavity  in  the  shoulder-blade  to  which  the 

head  of  the  humerus  is  jointed. 

GNATH'ITES  (Gr.  gnathos,  a  jaw).    The  masticatory  organs  of  Crustacea. 
GON-O-BLAS-TID'I-A  (Gr.  gonos.  offspring ;  blastidion,  dim.  of  blastos,  a  bud). 

The  processes  which  carry  the  reproductive  receptacles,  or  "  gonophores," 

in  many  of  the  Hydrozoa. 
GON-O-CA'LYX  (Gr.  gonos ;  and  Tcalux,  cup).   The  swimming-bell  in  a  medusi- 

form  gonophore,  or  the  same  structure  in  agonophore  which  is  not  detached. 
GON'O-PHORE  (Gr.  gonos  ;  andphero,  I  carry).     The  generative  buds,  or  recep- 
tacles of  the  reproductive  elements,  in  the  Hydrozoa,  whether  these  become 

detached  or  not. 
GON'O-SOME  (Gr.  gonos;  and  soma,  body).     Applied  as  a  collective  term  to 

the  reproductive  zooids  of  a  Hydrozoon. 
GON-O-THE'OA  (Gr.  gonos  /  and  theke,  a  case).     The  chitinous  receptacle  within 

which  the  gonophores  of  certain  of  the  Hydrozoa  are  produced. 
GRAL-LA-TO'RES  (Lat.  grallce,  stilts).     The  order  of  the  long-legged  Wading- 

Birds. 
GRA-NIV'O-ROUS  (Lat.  granum,  a  grain  or  seed ;  voro,  I  devour).    Living  upon 

grains  or  other  seeds. 
GRAP-TO-LIT'I-D^  (Gr.  grapTio,  I  write ;  lifhos,  stone).     An  extinct  sub-class 

of  the  Hydrozoa. 
GREG-A-RIN'I-DA  (Lat.  gregarius,  occurring  in  numbers  together).    A  class  of 

the  Protozoa. 
GUARD.     The  cylindrical  fibrous  sheath  with  which  the  internal  chambered 

shell  (phragmacone)  of  a  Belemnite  is  protected. 
GUI/ LET. 
GYM-NO-LJE'MA-TA  (Gr.  gumnos,  naked  ;  laimos,  the  throat).    An  order  of  the 


334  GLOSSARY. 

Polyzoa  in  which  the  mouth  is  devoid  of  the  valvular  structure  known  as 

the  "  epistome." 
GYM-NO-PHI' O-NA  (Gr.  gumnos,  naked;  ophis,  a  snake).    The  order  of  the 

Amphibia,  comprising  the  snake-like  Cwtilice. 
GYM-NOPH-THAL'MA-TA  (Gr.  gumnos  f  and  ophthalmof,  the  eye).     Applied  by 

Edward  Forbes  to  those  Medusae  in  which  the  eve-specks  at  the  margin  of 

the  disc  are  unprotected.    The  division  is  now  abandoned. 
GYM-NO-SO'MA-TA  (Gr.  gumnos  ;  and  somo,  the  body).     The  order  of  Pteropoda 

in  which  the  body  is  not  protected  by  a  shell. 
GYN'O-PHORES  (Gr.  gune,  woman ;  phero,  I  carry).     The  generative  buds,  or 

gonophores,  of  Hydrozoa,  which  contain  ova  alone,  and  differ  in  form  from 

those  which  contain  spermatozoa. 
GY-KEN-CEPH'A-LA  (Gr.  guroo,  I  wind  about  j  egTcephalos,  brain).     Applied  by 

Owen  to  a  section  of  the  Mammalia  in  which  the  cerebral  hemispheres  are 

abundantly  convoluted. 

ILa'MAL  (Gr.  haima,  blood).  Connected  with  the  blood-vessels,  or  with  the 
circulatory  system. 

H.E-MA-TOC  RY-A  (Gr.  haima,  blood ;  kruos,  cold).  Applied  by  Owen  to  the 
"cold-blooded"  Vertebrates— viz.,  the  Fishes,  Amphibia,  and  Reptile*. 

HJS-MA-TO-THER'MA  (Gr.  haima,  blood  ;  thermos,  warm).  Applied  by  Owen  to 
the  "warm-blooded"  Vertebrates— viz.,  Birds  and  Mammals. 

HAL'LUX  (Lat.  allex,  the  thumb  or  great  toe).  The  innermost  of  the  five 
digits  which  normally  compose  the  hind  foot  of  a  Vertebrate  animal.  In 
man,  the  great  toe. 

HAL-TE'KES  (Gr.  halteres,  weights  used  by  athletes  to  steady  themselves  in 
leaping).  The  rudimentary  filaments  or  "  balancers  "  which  represent  the 
posterior  pair  of  wings  in  the  Diptera,  an  order  of  Insects. 

HAUS'TEL-LATE  (Lat.  haurio,  I  drink).  Adapted  for  sucking  or  pumping  up 
fluids  ;  applied  to  the  mouth  of  certain  Crustacea  and  Insecta. 

HEC-TO-COT  Y-LTJS  (Gr.  hekaton,  a  hundred ;  Icotulos,  a  cup).  The  metamor- 
phosed reproductive  arm  of  certain  of  the  male  Cuttle-fishes.  In  the 
Argonaut  the  arm  becomes  detached,  and  was  originally  described  as  a 
parasitic  worm. 

HEL'MIN-THOID  (Gr.  helmins,  an  intestinal  worm).     "Worm-shaped,  vermiform. 

HE-MEI/Y-TRA  (Gr.  hemi,  half;  elutrpn,  a  sheath).  The  wings  of  certain  In- 
sects, in  which  the  apex  of  the  wing  is  membranous,  while  the  inner  por- 
tion is  chitinous,  and  resembles  the  elytron  of  a  beetle. 

HEM-I-MET-A-BOL'IO  (Gr.  hemi,  half;  metabole,  change).  Applied  to  those 
insects  which  undergo  an  incomplete  metamorphosis. 

HE-MIP'TE-RA  (Gr.  hemi;  and  pteron,  wing).  An  order  of  insects  in  which 
the  anterior  wings  are  sometimes  "  hemelytra." 

HER-MAPH'RO-DITE  (Gr.  Hermes,  Mercury;  Aphrodite,  Venus).  Possessing 
the  characters  of  both  sexes  combined. 

HET-E-RO-CER'CAL  (Gr.  heteros,  diverse  ;  Icerkos,  tail).  Applied  to  the  tail  of 
Fishes  when  it  is  unsymmetrical,  or  composed  of  two  unequal  lobes. 

HET-E-RO-GE'NE-ODS. 

HET-E-RO-GAN'GLI-ATE  (Gr.  heteros,  diverse ;  gagglion,  a  knot).  Possessing  a 
nervous  system  in  which  the  ganglia  are  scattered  and  unsymmetrical  (as 
in  the  Mollusca,  for  example). 

HET-E-RO-MOR'PHIC  (Gr.  heteros;  morphe.form).    Differing  in  form  or  shape. 

HET-E-ROPH'A-GI  (Gr.  heteros,  other;  phago,  I  eat).  Applied  to  Birds  the 
young  of  which  are  born  in  a  helpless  condition,  and  require  to  be  fed  by 
the  parents  for  a  longer  or  shorter  period. 

HET-E-ROP'O-DA. 

HEX'A-POD  (Gr.  hexa,  six ;  pous,  foot).  Possessing  six  legs ;  applied  to  the 
Insecta. 

HI'LUM  (Lat.  hilum,  a  little  thing).  A  small  aperture  (as  in  the  gemmules  of 
sponges),  or  a  small  depression  (as  in  Noctiluca). 

HIR-U-DIN'E-A  (Lat.  hirudo,  a  horse-leech).  The  order  of  Annelida  com- 
prising the  Leeches. 


GLOSSARY.  335 

HIS-TOI/O-GY  (Gr.  hiatos,  a  web ;  logos,  a  discourse).    The  study  of  the  tissues ; 

more  especially  of  the  minuter  elements  of  the  body. 
HOL-O-CEPH'A-LI  (Gr.   holes,  whole ;  kephale,  head).     A  sub-order  of  the 

Elasmobranchii,  comprising  the  Chimcerce. 
HOL-O-MET-A-BOL'IC  (Gr.  holos,  whole;  metabole,  change).     Applied  to  insects 

which  undergo  a  complete  metamorphosis. 
HOL-O-STO'MA-TA  (Gr.  holos.  whole ;  stoma,  mouth).     A  division  of  Gasteropo- 

dous  Molluscs,  in  which  the  aperture  of  the  shell  is  rounded,  or  "entire." 
HOL-O-THU-ROI'DE-A  (Gr.  holos;  thura,  door ;  and  eidos,  form).    An  order  of 

Echinodermata  comprising  the  Trepangs. 
HOM-O-CEK'CAL  (Gr.  homos,  same ;  kerkos,  tail).    Applied  to  the  tail  of  Fishes 

when  it  is  symmetrical,  or  composed  of  two  equal  lobes. 
HO-MO  -  GE'NE-OUS. 
HO-MO-GAN'GLI-ATE  (Gr.  homos,  same ;  gagglion,  a  knot).    Having  a  nervoua 

system  in  which  the  ganglia  are  symmetrically  arranged  (as  in  the  Annu- 

losa,  for  example). 
HO-MOL'O-GOUS  (Gr.  homos  ;  and  logos,  a  discourse).    Applied  to  parts  which 

are  constructed  upon  the  same  fundamental  plan. 
HO-MO-MOR'PHOUS  (Gr.  homos;  and  morphe,  form).    Having  a  similar  external 

appearance  or  form. 

HU'ME-BUS.    The  bone  of  the  upper  arm  (brachium)  in  the  Vertebrates. 
HY'A-LINE  (Gr.  hualos,  crystal).     Crystalline  or  glassy. 
HYD'-A-TIDS  (Gr.  hudatis,  a  vesicle).     The  vesicle  containing  the  larval  forms 

(Echinococci}  of  the  tapeworm  of  the  dog. 

HY'DRA-FORM.    Kesembhng  the  common  fresh-water  polype  {Hydra}  in  form. 
HY'DRA. 
HY-DRO-CATT'LTJS  (Gr.  hudra,  a  water-serpent ;  and  kaulos,  a  stem).    The  main 

stem  of  the  coenosarc  of  a  Hydrozopn. 
HY'-DRO-CYSTS  (Gr.  hudra  ;  and  kustis,  a  cyst).     Curious  processes  attached  to 

the  coenosarc  of  the  Physophoridce,  and  termed  "  feelers  "  (Fuhler  and  Taster 

of  the  Germans). 
HY-DRCE'CI-UM  (Gr.  hudra  ;  and  oikos,  a  house).     The  chamber  into  which  the 

coenosarc  in  many  of  the  Calycophoridce  can  be  retracted. 
HY-DROI'DA  (Gr.  hudra  ;  and  eidos,  form).    The  sub-class  of  the  Hydrozoa, 

which  comprises  the  animals  most  nearly  allied  to  the  Hydra. 
HY-DRO-PHYL'LI-A  (Gr.  hudra;  and  phullon,  a  leaf).     Overlapping  append- 
ages or  plates  which  protect  the  polypites  in  some  of  the  oceanic  Hydrozoa 

(Calycophoridce  and  Physophoridce).     They  are  often  termed  "  bracts,"  and 

are  the  Deckstucke  of  the  Germans. 
HY-DRO-RHI'ZA  (Gr.  hudra;  and  rhiza,  root).    The  adherent  base  or  proximal 

extremity  of  any  Hydrozoon. 
HY-DRO-SO'MA  (Gr.  hudra;  and  soma,  body).    The  entire  organism  of  any 

HydrozoiJn. 
HY-DRO-THE'CA  (Gr.  Jiudra  f  and  theke,  a  case).    The  little  chitinous  cups  in 

which  the   polypites    ot    the    Sertularida  and  Campanularida  are    pro- 
tected. 
HY-DRO-ZO'A  (Gr.  hudra  ;  and  zoon,  animal).    The  class  of  the  Cwlenterata, 

which  comprises  animals  constructed  after  the  type  of  the  Hydra. 
HY-MEN-OP'TER-A  (Gr.  humen,  a  membrane ;  pteron,  a  wing).    An  order  of 

Insects  (comprising  Bees,  Ants,  etc.)  characterized  by  the  possession  of  four 

membranous  wings. 

HY'OID  (Gr.  Y  /  eidos,  form).    The  bone  which  supports  the  tongue  in  Ver- 
tebrates, and  derives  its  name  from  its  resemblance  in  man  to  the  Greek 

letter  Y. 
HY'PO-STOME  (Gr.  hupo,  under ;  stoma,  mouth).    The  upper  lip,  or  "  labrum," 

of  certain  Crustacea  (e.  g.,  Trilobites). 

HY-RA-COID'E-A  (Gr.  hurax,  a  shrew;  eidos,  form).     An  order  of  the  Mam- 
malia constituted  for  the  reception  of  the  single  genus  Hyrax. 

IOH-THY-O-DOR'Y-LITB  (Gr.  ichthus,  fish;  doru,  spear;  lithos,  stone).    The 
fossil  fin-spines  of  Fishes. 


336  GLOSSARY. 

ICH-THY-O-MOR'PHA  (Gr.  ichthus  ;  morphe,  shape).     An  order  of  Amphibians, 

often  called  Urodela,  comprising  the  fish-like  frewts,  etc. 
ICH-THY-OPH-THI'BA  (Gr.  ichthus  /  phtheir,  a  louse).    An  order  of  Crustacea 

comprising  animals  which  are  parasitic  upon  Fishes. 
ICH-THY -OP' SI-DA  (Gr.  ichthus;  opsis,  appearance).     The  primary  division  of 

Vertebrata,  comprising  the  Fishes  ana  Amphibia.     Often  spoken  of  as  the 

Branchiate  Vertebrata. 
ICH-THY-OP-TER-YG'I-A  (Gr.  ichthus;  pterux,  wing).    An  extinct  order  of 

Eeptiles. 
ICH-THY-O-SAU'BI-A  (Gr.  ichthus ;  saura,  lizard).     Synonymous  with  Ichthy- 


II/I-TJM.  The  haunch-bone,  one  of  the  bones  of  the  pelvic  arch  in  the  higher 
Vertebrates. 

I-MA'OO  (Lat.  for  an  image  or  apparition).  The  perfect  insect,  after  it  has 
undergone  its  metamorphoses. 

IM'BRI-CA-TED.  Applied  to  scales  or  plates  which  overlap  one  another  like 
tiles. 

IN-CI'SOR  (Lat.  incido,  I  cut).  The  cutting  teeth  fixed  in  the  intermaxillary 
bones  of  the  Mammalia,  and  the  corresponding  teeth  in  the  lower  jaw. 

TN-E-QUI-LAT'ER-AL.  Having  the  two  sides  unequal,  as  in  the  case  of  the 
shells  of  the  ordinary  bivalves  (Lamellibranchiata).  When  applied  to  the 
shells  of  the  Foraminifera,  it  implies  that  the  convolutions  of  the  shell  do 
not  lie  in  the  same  plane,  but  are  obliquely  wound  round  an  axis. 

IN-E'QUI- VALVE.    Composed  of  two  unequal  pieces  or  valves. 

IN-FUN-DIB'U-LTJM  (Lat.  for  funnel).  The  tube  formed  by  the  coalescence  or 
apposition  of  the  epipodia  in  the  Cephalopoda — commonly  termed  the 
"  funnel,"  or  "  siphon." 

IN-FU-SO'RI-A  (Lat.  infusum,  an  infusion).  A  class  of  Protozoa,  so  called  be- 
cause they  are  often  developed  in  organic  infusions. 

IN'GUIN-AL  (Lat.  inguen,  groin).    Connected  with,  or  situated  upon,  the  groin. 

IH--O-PER-CU-LA'TA  (Lat.  ^n,  without;  operculum,  a  lid).  The  division  of  pul- 
monate  Gasteropoda  in  which  there  is  no  shelly  or  horny  plate  (operculum) 
by  which  the  shell  is  closed  when  the  animal  is  withdrawn  within  it. 

IN-SEC'TA  (Lat.  inseco,  I  cut  into).  The  class  of  Articulate  animals  commonly 
known  as  Insects. 

IN-SEC-TIV'O-RA  (Lat.  insectum,  an  insect;  voro,  I  devour).  An  order  of 
Mammals. 

IN-SEC-TIV'O-ROITS.    Living  upon  Insects. 

IN-SES-SO'RES  (Lat.  insideo,  I  sit  upon).  The  order  of  the  Perching  Birds, 
often  called  Passeres. 

IN-TER-AM-BU-LA'CRA  (Lat.  inter,  between ;  ambulacrum,  that  which  serves 
for  walking).  The  rows  of  plates  in  an  Echinoderm,  which  are  not  per- 
forated for  the  emission  of  the  "  tube-feet." 

IN-TER-MAX-IL'L^;,  or  PRJS-MAX-IL'LJS  (Lat.  inter,  between;  prce,  before; 
maxilla,  the  jaw).  The  two  bones  which  are  situated  between  the  two 
superior  maxillae  in  Vertebrata.  In  man,  and  some  monkeys,  the  prsemax- 
illae  anchylose  with  the  maxillae,  so  as  to  be  irrecognizable  m  the  adult. 

IN-TUS-SUS-CEP'TION  (Lat.  mtu6}  within;  suscipio,  I  take  up).  The  act  of 
taking  foreign  matter  into  a  living  being. 

IN-VER-TE-BRA^TA  (Lat.  in,  without ;  vertebra,  a  bone  of  the  back).  Animals 
without  a  spinal  column  or  backbone. 

IS'CHI-UM  (Gr.  ischion,  the  hip).  One  of  the  bones  of  the  pelvic  arch  in  Ver- 
tebrates. 

I-SOP'O-DA  (Gr.  isos,  equal ;  podes,  feet).  An  order  of  Crustacea  in  which  the 
feet  are  like  one  another  and  equal. 

JU'GTJ-LAB  (Lat.  jugulum,  the  throat).  Connected  with,  or  placed  upon,  the 
throat.  Applied  to  the  ventral  fins  of  fishes  when  they  are  placed  beneath 
or  in  advance  of  the  pectorals. 

KAI-NO-ZO'IO  (Gr.  Jcainos,  recent ;  zoe,  life).    The  Tertiary  period  in  Geology, 


GLOSSARY.  337 

comprising  those  formations  in  -which  the  organic  remains  approximate 

more  or  less  closely  to  the  existing  fauna  and  flora. 
KER'A-TODE  (Gr.  keras,  horn;  eidos,  form).    The  horny  substance  of  which 

the  skeleton  of  many  sponges  is  made  up. 
KER-A-TO'SA.    The  division  of  Sponges  in  which  the  skeleton  is  composed 

of  keratode. 

LA'BI-UM  (Lat.  for  lip).  Restricted  to  the  lower  lip  of  Articulate  animals. 
LA'BEUM  (Lat.  for  lip).  Restricted  to  the  upper  lip  of  Articulate  animals. 
LAB-Y-RINTH-O-DON'TI-A  (Gr.  laburinthos,  a  labyrinth ;  odous,  tooth).  An 

extinct  order  of  A mphibia,  so  called  from  the  complex  microscopic  structure 

of  the  teeth. 
LAC-ER-TIL'I-A  (Lat.  lacerta,  a  lizard).     An  order  of  Reptilia  comprising  the 

Lizards  and  Slow-worms. 
L^E-MO-DIP'O-DA  (Gr.  laimos,  throat ;  dis,  twice ;  podes,  feet).    An  order  of 

Crustacea,  so  called  because  they  have  two  feet  placed  far  forward,  as  it 

were  under  the  throat. 
LA-MEL-IJ-BRANCH-I-A'TA  (Lat.  lamella,  a  plate;   Gr.  bragchia,  gills).    The 

class  of  Mollusca,  comprising  the  ordinary  bivalves,  characterized  by  the 

possession  of  lamellar  gills. 
LA-MEL-LI-ROS'TRES  (Lat.  lamella,  a  plate ;  rostrum,  beak).    The  flat-billed 

Swimming  Birds  (Natatores],  such  as  Ducks,  Geese,  Swans,  etc. 
LAR'VA  (Lat.  for  a  mask).    The  insect  in  its  first  stage  after  its  emergence 

from  the  egg,  when  it  is  usually  very  different  from  the  adult. 
LAR'TNX.    The  upper  part  of  the  windpipe,  forming  a  cavity  with  appropriate 

muscles  and  cartilages,  situated  beneath  the  hyoid  bone,  and  concerned  in 

Mammals  in  the  production  of  vocal  sounds. 
LEN-TIC'U-LAR  (Lat.  lens,  a  bean).    Shaped  like  a  biconvex  lens. 
LEP-I-DOP'TE-RA  (Gr.  lepis,  a  scale ;  pteron,  a  wing).    An  order  of  Insects, 

comprising  Butterflies  and  Moths,  characterized  by  possessing  four  wings 

which  are  usually  covered  with  minute  scales. 
LEP-I-DO'TA  (Gr.  lepidotos,  covered  with  scales).    Formerly  applied  to  the 

order  Dipnoi,  containing  the  Mud-fishes  (Lepidosireri). 
LEP-TO-CAR'DI-A  (Gr.  leptos,  slender,  small;  Icardia,  heart).    The  name  given 

by  Miiller  to  the  order  of  fishes  comprising  the  Lancelot,  now  called  Pha- 

ryngobranchii. 
LIG-A-MEN'TUM  NTJ'CBLE  (Fr.  nuque,  the  nape  of  the  neck).     The  band  of  elastic 

fibres  by  which  the  weight  of  the  head  in  Mammalia  is  supported. 
LIN'GUAL  (Lat.  lingua,  the  tongue).    Connected  with  the  tongue. 
LIN'GU-LA  (Lat.  lingula,  a  little  tongue).    The  upper  flexible  portion  of  the 

labium  or  lower  lip  in  Insects. 
LIS-SEN-CEPH'A-LA  (Gr.  lissos,  smooth ;  eglcephalos,  brain).    A  primary  division 

of  Mammalia,  according  to  Owen,  in  which  the  cerebral  hemispheres  are 

smooth  or  have  few  convolutions. 


LITH'O-CYSTS  (Gr.  Uthos,  a  stone ;  Jcustis.z  cyst).  The  sense-organs  or  "mar- 
ginal bodies"  of  the  Lucernarida  or  SteganopMhalmate  Medusae,. 

LON-GI-PEN-NA'T^E  (Lat.  longus,  long ;  penna,  wing).  A  group  of  the  Nata- 
torial Birds. 

LON-GI-ROS'TRES  (Lat.  longus  /  rostrum,  beak).    A  group  of  the  Wading  Birds. 


order  of  Crustacea. 
LO-RI'CA  (Lat.  for  a  breast-plate).    Applied  to  the  protective  case  with  which 

certain  Infusoria  are  provided.. 
LOR-I-CA'TA  (Lat.  lorica}  a  cuirass).    The  division  of  Reptiles  comprising  the 

Chelonia  and  Crocod^Ua,  in  which  bony  plates  are  developed  in  the  skin 

(derma). 

LU-CER-NAR'I-DA  (Lat.  lucerna,  a  lamp).    An  order  of  the  Hydrozoa. 
LUM'BAR  (Lat.  himbus,  loin).    Connected  with  the  loins. 
LU'NATE  (Lat.  luna,  moon).    Crescentic  in  shape. 


S38  GLOSSARY. 

LY-EN-CEPH'A-LA  (Gr.  luo,  I  loose ;  egTcephalos,  brain).  A  primary  division 
of  Mammals,  according  to  Owen. 

MAC-RO-DAC'TY-LI  (Gr.  malcros,  long;  daTctulos,  a  finger).  A  group  of  the 
Wading  Birds. 

MA-CRU'RA  (Gr.  mdkros,  long;  oura,  tail).  A  tribe  of  Decapod  Crustaceans 
with  long  tails  (e.  g.,  the  Lobster,  Shrimp,  etc.). 

MAD-RE-POR'I-FORM.  Perforated  with  small  holes,  like  a  coral ;  applied  to  the 
tubercle  by  which  the  ambulacral  system  of  the  Echinoderms  mostly  com- 
municates with  the  exterior. 

MAX-A-CO-DERM'A-TA. 

MAL-A-COS'TRA-CA  (Gr.  malakos,  soft;  ostrakon,  shell).  A  division  of  Crus- 
tacea. Originally  applied  by  Aristotle  to  the  entire  class  Crustacea,  because 
their  shells  were  softer  than  those  of  the  Mollusca. 

MAL-LOPH'A-GA  (Gr.  mallos,  a  fleece;  phago,  I  eat).  An  order  of  Insects 
which  are  mostly  parasitic  upon  birds. 

MAM-MA'LIA  (Lat.  mamma,  the  breast).  The  class  of  Vertebrate  animals 
which  suckle  their  young. 

MAN'DI-BLE  (Lat.  mandibuLum,  a  jaw).  The  upper  pair  of  jaws  in  Insects  -, 
also  applied  to  one  of  the  pairs  of  jaws  in  Crustacea  and  Spiders,  to  the  beak 
of  Cephalopoda,  the  lower  jaw  of  Vertebrates,  etc. 

MAN'TLE.  The  external  integument  of  most  of  the  Mollusca,  which  is  largely 
developed,  and  forms  a  cloak  in  which  the  viscera  are  protected.  Techni- 
cally called  the  "  pallium." 

MA-NU'BRI-UM  (Lat.  for  a  handle).  The  polypite  which  is  suspended  from 
the  roof  of  the  swimming-bell  of  a  Medusa,  or  from  the  gonocalyx  of  a 
medusiform  gonophore  among  the  Hydrozoa. 

MA'NUS  (Lat.  for  the  hand).    The  hand  of  the  higher  Vertebrates. 

MAR-SIP-O-BRANCH'I-I  (Gr.  marsipos,  a  pouch ;  bragc/iia,  gills).  The  order  of 
Fishes  comprising  the  Hag-fishes  and  Lampreys,  with  pouch-like  gills. 

MAR-SU-PI-A'LI-A  (Lat.  marsupium,  a  pouch).  An  order  of  Mammals  in  which 
the  females  mostly  have  an  abdominal  pouch  in  which  the  young  are  carried. 

MAS'TAX  (Gr.  for  mouth).  The  muscular  pharynx  or  u  buccal  tunnel"  into 
which  the  mouth  opens  in  most  of  the  Eotifera. 

MAS-TI-CA'TO-RY  (Lat.  mastico,  I  chew).    Applied  to  parts  adapted  for  chewing. 

MAX-IL'L^E  (Lat.  for  jaws).  The  inferior  pair  or  pairs  of  jaws  in  the  Arthro- 
poda  (Insects,  Crustacea,  etc.).  The  upper  jaw-bones  of  Vertebrates. 

MAX-IL  LI-PEDES  (Lat.  maxilla,  jaws ;  peg,  the  foot).  The  limbs  in  Crustacea 
and  Myriapoda  which  are  converted  into  masticatory  organs,  and  are  com- 
monly called  "  foot-jaws." 

ME-DUL'LA  (Lat.  for  marrow).  Applied  to  the  marrow  of  bones,  or  to  the 
spinal  cord,  with  or  without  the  adjective  "  spinal'ig." 

ME-DU'S.E.  An  order  of  Hydrozoa,  commonly  Known  as  Jelly-fishes  (Disco- 
pJiora,  or  AcalepJuz),  so  called  because  of  the  resemblance  of  their  tentacles 
to  the  snaky  hair  of  the  Medusa.  Many  Medusae  are  now  known  to  be 
merely  the  gonophores  of  Hydrozoa. 

ME-DU'SI-FORM.    Eesembling  a  Medusa  in  shape. 

ME-DU'SOID.  Like  a  Medusa  ;  used  substantively  to  designate  the  medusiform 
gonophores  of  the  Hydrozoa. 

MEM-BRA'NA  KIC'TI-TANS  (Lat.  nicto,  I  wink).    The  third  eyelid  of  Birds,  etc. 

MEN'TUM  (Lat.  for  the  chin).  The  basal  portion  of  the  laoium  or  lower  lip 
in  Insects. 

ME-RO-STOM'A-TA  (Gr.  meron,  thigh;  stoma,  mouth).  An  order  of  Qnutaeta 
in  which  the  appendages  which  are  placed  round  the  mouth,  and  which 
officiate  as  jaws,  have  their  free  extremities  developed  into  walking  or  pre- 
hensile organs. 

MES-EN-TE'RI-ES  (Gr.  mesos,  intermediate ;  enteron,  intestine).  In  a  restricted 
sense,  the  vertical  plates  which  divide  the  somatic  cavity  of  a  Sea-anemone 
(Actinia}  into  chambers. 

MES-O-PO'DI-UM  (Gr.  mesos,  middle;  pous,  foot).  The  middle  portion  of  the 
"foot  "of  Molluscs. 


GLOSSARY.  339 

MES-O-STER'NTTM  (Gr.  mesos,  intermediate  5   sternon,  the  breast-bone).    The 
middle  portion  of  the  sternum,  intervening  between  the  attachment  of  the 
second  pair  of  ribs  and  the  xiphoid  cartilage  (xiphisternum). 
MES-O-THO'RAX  (Gr.  mesos;  and  thorax,  the  chest).    The  middle  ring  of  the 
thorax  in  Insects. 

MES-O-ZO'IC  (Gr.  mesos ;  zoe,  life).    The  Secondary  period  in  Geology. 

MET-A-CAR'PUS  (Gr.  meta,  after ;  karpos,  the  wrist).  The  bones  which  form 
the  "root  of  the  hand,"  and  intervene  between  the  wrist  and  the  fingers. 

MET-A-MOR'PHO-SIS  (Gr.  meta,  implying  change ;  morphe,  shape}.  ^  The  changes 
of  form  which  certain  animals  undergo  in  passing  from  their  younger  to 
their  fully-grown  condition. 

MET-A-PO'DI-UM  (Gr.  meta,  after;  pous.  the  foot).  The  posterior  lobe  of  the 
foot  in  Mollusca  ;  often  called  the  "  operculigerous  lobe,"  because  it  de- 
velops the  operculum  when  this  structure  is  present. 

ME-TAS'TO-MA  (Gr.  meta,  after;  stoma,  mouth).  The  plate  which  closes  the 
mouth  posteriorly  in  the  Crustacea. 

MET-A-TAR'SUS  (Gr.  meta,  after;  tarsos,  the  instep).  The  bones  which  inter- 
vene between  the  bones  of  the  ankle  (tarsus)  and  the  digits  in  the  hind-foot 
of  the  higher  Vertebrates. 

MET-A-THO'RAX  (Gr.  meta,  after;  thorax,  the  chest).  The  posterior  ring  of 
the  thorax  in  Insects. 

MI-MET'IO  (Gr.  mimetikos,  imitative).  Applied  to  organs  or  animals  which 
resemble  each  other  in  external  appearance,  but  not  in  essential  structure. 

MO'LARS  (Lat.  mola,  a  mill).  The  "  grinders  "  in  man,  or  the  teeth  in  diphyo- 
dont  Mammals  which  are  not  preceded  by  milk-teeth. 

MOL-LUS'CA  (Lat.  mollis,  soft).  The  sub-kingdom  which  includes  the  Shell- 
fish proper,  the  Pblyzoa,  the  Tunicata,  and  the  Lamp-shells ;  so  called  from 
the  generally  soft  nature  of  their  bodies. 

MOL-LUS-COI'DA  (Mollusea  ;  Gr.  eidos,  form).  The  lower  division  of  the  Mol- 
lusca,  comprising  the  Polyzoa,  Tunicata,  and  Brachiopoda. 

MON'ADS  (Gr.  monas,  unity).  Microscopical  organisms  of  an  extremely  simple 
character,  developed  in  organic  infusions. 

MO-NOC'U-LOUS  (Gr.  monos,  single  ;  Lat.  ooulus,  eye).  Possessed  of  only  one 
eye. 

MOX-O-DELPH'I-A  (Gr.  monos,  single ;  delphus,  womb).  The  division  of  Mam- 
malia, in  which  the  uterus  is  single. 

MO-NCE'OI-OUS  (Gr.  monos,  single ;  oikos,  house).  Applied  to  individuals  in 
which  the  sexes  are  united. 

MON-O-MY'A-RY  (Gr.  monos,  single ;  mus,  muscle).  Applied  to  those  bivalves 
(Lamellibmnchiata)  in  which  the  shell  is  closed  by  a  single  adductor  muscle. 

MON-O-PHY'O-DONT  (Gr.  monos  ;  phuo,  I  generate  ;  odpus,  tooth).  Applied  to 
those  Mammals  in  which  only  a  single  set  of  teeth  is  ever  developed. 

MOX-O-THAL'A-MOUS  (Gr.  monos  /  andthalamos,  chamber).  Possessing  only  a 
single  chamber.  Applied  to  the  shells  of  Foraminifera  and  Mollusca. 

MON-O-TREM'A-TA  (Gr.  monos  ;  trema,  aperture).  The  order  of  Mammals  com- 
prising the  Duck-mole  and  Echidna,  in  which  the  intestinal  canal  opens 
into  a  "  cloaca"  common  to  the  ducts  of  the  urinary  and  generative  organs. 

MUL-TI-LOC'U-LAR  (Lat.  multi,  many ;  loculus,  a  little  purse).  Divided  into 
many  chambers. 

MUL'TI-VALVE.    Applied  to  shells  which  are  composed  of  many  pieces. 

MUL-^TUN'GU-LA  (Lat.  multi,  many;  ungula,  hoof).  The  division  of  Perisso- 
dactyle  Ungulates,  in  which  each  foot  has  more  than  a  single  hoof. 

MY'E-LON  (Gr.  muelos,  marrow).    The  spinal  cord  of  Vertebrates. 

MYR-I-AP'O-DA  (Gr.  murioi,  ten  thousand ;  podes,  feet).  A  class  of  Arthropoda 
comprising  the  Centipedes  and  their  allies,  characterized  by  their  numerous 
feet. 

NA'CRE-OUS  (Fr.  nacre,  mother-of-pearl,  originally  Oriental).    Pearly ;  of  the 

texture  of  mother-of-pearl. 

NAT-A-TO'RES  (Lat.  nare,  to  swim).    The  order  of  the  Swimming  Birds. 
NA'TA-TO-EY  (Lat.  nare,  to  swim).    Formed  for  swimming. 


340  GLOSSARY. 

NATJ'TI-LOID*.    Resembling  the  shell  of  the  Nautilus  in  shape. 

NECH-O-CAL'Y-CES. 

NECH-O-CA'LYX  (Gr.  necho,  I  swim;  kalux,  cup).  The  swimming-bell  01 
"  disc"  of  a  Medusa  or  Jelly-fish. 

NEM-A-TEL'MI-A  (Gr.  nema,  thread ;  helmins,  a  worm).  The  division  of  Scale- 
cida  comprising  the  Bound-worms,  Thread-worms,  etc. 

NE-MAT'O-CYSTS  (Gr.  n'ema,  thread ;  kustis,  a  bag).  The  thread-cells  of  the 
Ccelenterata.  (See  Cnidae.) 

NEM-A-TO'DA. 

NEM-A-TOID'E-A  (Gr.  n'ema,  thread;  eidos,  form).  An  order  of  Scolecida  com- 
prising the  Thread-worms,  Vinegar-eels,  etc. 

NE-MAT'O-PHORES  (Gr.  nema,  thread :  phero,  I  carry).  Caecal  processes  found 
on  the  coenosarc  of  certahi  of  the  Sertularida,  containing  numerous  thread- 
cells  at  their  extremities. 

NE-MER'TI-DA  (Gr.  Nemertes,  proper  name).  A  division  of  the  Turbellarian, 
Worms,  commonly  called  "  Ribbon-worms." 

NEBV'UBES  (Lat.  nervus,  a  sinew).  The  ribs  which  support  the  membranous 
wings  of  insects. 

NEU'BAL  (Gr.  neuron,  a  nerve).    Connected  with  the  nervous  system. 

.NEU-RA-POPH'Y-SIS  (Gr.  neuron,  a  nerve ;  apophusis,  a  projecting  part).  The 
"  spinous  process  "  of  a  vertebra,  or  the  process  formed  at  the  point  of 
junction  of  the  neural  arches. 

.NEUB-O-PO'DI-UM  (Gr.  neuron,  a  nerve ;  pous,  the  foot).  The  ventral  or  in- 
ferior division  of  the  "foot  tubercle"  of  an  Annelide;  often  called  the 
"ventral  oar." 

NEU-BOP'TE-RA  (Gr.  neuron, ;  and  pteron,  a  wing).  An  order  of  Insects  charac- 
terized by  four  membranous  wings  with  numerous  reticulated  nervures 
(e.  g.,  Dragon-flies). 

NEU'TEB  (Lat.  for  neither  the  one  nor  the  other).  Having  no  fully-developed 
sex. 

NID-I-FI-CA'TION  (Lat.  nidus,  a  nest ;  facio,  I  make).    The  building  of  a  nest. 

NOC-TUB'NAL  (Lat.  nox,  night).    Applied  to  animals  which  are  active  by  night. 

NOB'MAL  (Lat.  norma,  a  rule).    Conforming  to  the  ordinary  standard. 

NO-TO-BRANCH-I-A'TA  (Gr.  notos,  the  back ;  and  bragchia,  gills).  Carrying  the 
gills  upon  the  back ;  applied  to  a  division  of  the  Annelida. 

NO'TO-CHOBD  (Gr.  notos,  back ;  cTiorde,  string).  A  cellular  rod  which  is  devel- 
oped in  the  embryo  of  Vertebrates  immediately  beneath  the  spinal  cord, 
and  which  is  usually  replaced  in  the  adult  by  the  vertebral  column.  Often 
it  is  spoken  of  as  the  "  chorda  dorsalis." 

NO-TO-PO'DI-UM  (Gr.  notos,  the  back;  and  pous,  the  foot).  The  dorsal  divis- 
ion of  one  of  the  foot-tubercles  or  parapodia  of  an  Annelide  ;  often  called 
the  "  dorsal  oar." 

NU'CLE-A-TED.    Possessing  a  nucleus  or  central  particle. 

ND-CLE'O-LUS.  1.  The  minute  solid  particle  in  the  ulterior  of  the  nucleus  of 
some  cells.  2.  The  minute  spherical  particle  attached  to  the  exterior  of 
the  u  nucleus,"  or  ovary,  of  certain  Infusoria,  performing  the  functions  of 
a  testicle. 

NU'OLE-US  (Lat.  nucleus,  a  kernel).  1.  The  solid  or  vesicular  bodv  found  in 
many  cells.  2.  The  solid  rod,  or  band-shaped  body,  found  in  the  interior 
of  many  of  the  Protozoa,  and  having,  in  certain  of  them,  the  functions  of 
an  ovary.  3.  The  " madreppriform  tubercle"  of  the  EcJiinodermata.  4. 
The  embryonic  shell  which  is  retained  to  form  the  apex  of  the  adult  shell 
in  many  of  the  Mollusca. 

NC-DI-BRANCH-I-A'TA  (Lat.  nudus,  naked;  and  Gr.  bragchia,  gills).  An  order 
of  the  Gasteropoda  in  which  the  gills  are  naked. 

NYMPHS.    The  active  pupse  of  certain  Insects. 

OC-CIP'I-TAL.    Connected  with  the  occiput,  or  the  back  part  of  the  head. 
O-CE-AN'IO.    Applied  to  animals  which  inhabit  the  open  ocean  (  =  pelagic). 
O-CEL'LI  (Lat.  diminutive  ofoculus,  eye).    The  simple  eyes  of  many  Echino- 
derms,  Spiders,  Crustaceans,  Molluscs,  etc. 


GLOSSARY.  341 

OO-TOP'O-DA  (Gr.  octo,  eight ;  pous,  foot).     The  tribe  of  Cuttle-fishes  with 

eight  arms  attached  to  the  head. 
O-DON-TO-CE'TI  (Gr.  odous,  tooth  ;  ketos,  whale).     The  "toothed"  "Whales,  in 

contradistinction  to  the  "  whalebone  "  Whales. 

O-DOX'TOID  (Gr.  odous  ;  eidos,  form).  The  "  odontoid  process  "  is  the  centrum 
or  body  of  the  first  cervical  vertebra  (atlas}.  It  is  detached  from  the  atlas, 
and  is  usually  anchylosed  with  the  second  cervical  vertebra  (axis},  and  it 
forms  the  pivot  upon  which  the  head  rotates. 

O-DON'TO-PHORE  (Gr.  odous,  tooth ;  phero,  I  carry).  The  so-called  "  tongue  " 
or  masticatory  apparatus  of  Gasteropoda,  Pteropoda,  and  Cephalopoda. 

(E-SOPH'A-GUS.    The  gullet  or  tube  leading  from  the  mouth  to  the  stomach. 

OL-I-GO-CH^'TA  (Gr.  oligoi,  few ;  chaite,  hair).  An  order  of  Annelida,  com- 
prising the  Earth-worms,  in  which  there  are  few  bristles. 

O-MA'SUM  (Lat.  for  bullock's  tripe).  The  third  stomach  of  Euminants,  com- 
monly called  the  psalterium,  or  many-plies. 

OM-NIV O-ROUS  (Lat.  omnia,  everything;  voro,  I  devour).  Feeding  indis- 
criminately upon  all  sorts  of  food. 

O-PER-CU-LA'TA  (Lat.  operculum,  a  lid).  A  division  of  pulmonate  Gasterop- 
oda, in  which  the  shell  is  closed  by  an  operculum. 

O-PER'CU-LTJM.  A  horny  or  shelly  plate  developed  in  certain  Mollusca  upon 
the  hinder  part  of  the  foot,  and  serving  to  close  the  aperture  of  the  shell 
when  the  animal  is  retracted  within  it ;  also  the  lid  of  the  shell  of  a  Bala.- 
n us  or  Acorn-shell;  also  the  chain  of  flat  bones  which  cover  the  gills  in 
many  fishes. 

O-PHID'I-A  (Gr.  ophidion,  a  little  snake).  The  order  of  Reptiles  comprising 
the  Snakes. 

OPH-I-DO-BA-TBA'CHI-A  (Gr.  ophis,  a  snake;  batrachos,  a  frog).  Sometimes  ap- 
plied to  the  order  of  Snake-like  Amphibians  comprising  the  Ccecilice. 

OPH-I-O-MOB'PHA  (Gr.  ophis;  morphe,  shape).  The  order  of  Amphibia  com- 
prising the  Ccecilice. 

OPH-I-U-ROID'E-A  (Gr.  ophis,  a  snake;  oura,  tail:  eidos,  form).  An  order  of 
Echinodermata  comprising  the  Brittle-stars  and  Sand-stars. 

O-PIS-THO-BRANCH-I-A'TA  (Gr.  opisthen,  behind ;  bragchia,  gills).  A  division 
of  Gasteropoda  in  which  the  gills  are  placed  on  the  posterior  part  of  the 
body. 

O-PIS-THO-CCE'LOTIS  (Gr.  opisthen,  behind;  Icoilos,  hollow).  Applied  to  verte- 
brae, the  bodies  of  which  are  hollow  or  concave  behind. 

ORAL  (Lat.  os.  mouth).     Connected  with  the  mouth. 

OR-NT-THO-DEL  PHI-A  (Gr.  ornis,  a  bird  ;  delphus,  womb).  The  primary  divis- 
ion of  Mammals  comprising  the  Monotremata. 

OR-THOP'TE-RA  (Gr.  orthos,  straight ;  pteron,  wing).    An  order  of  Insects. 

OS'CU-LA  (Lat.  diminutive  of  os,  mouth).  1.  The  large  apertures  by  which  a 
sponge  is  perforated  ("  exhalant  apertures").  2.  The  suckers  with  which 
the  Tceniada  (Tape-worms  and  Cystic  Worms)  are  provided. 

OS-SIO'U-LA  (Lat.  diminutive  of  os,  bone).  Literally,  small  bones.  Often  used 
to  designate  any  hard 'structures  of  small  size,  such  as  the  calcareous  plates 
in  the  integument  of  the  Star-fishes. 

OS-TRA-CO'DA  (Gr.  ostrakon,  a  shell ;  and  eidos,  form).  An  order  of  small 
Crustaceans  which  are  enclosed  in  bivalve  shells. 

OT'O-LITHS  (Gr.  ous,  ear ;  and  lithos,  stone).  The  calcareous  bodies  connected 
with  the  sense  of  hearing,  even  in  its  most  rudimentary  form. 

O-VA'RI-AN  VES-I-CLES  or  CAP'SULES.     The  generative  buds  of  the  Sertularida. 

O'VA-RY  (O-VA'RI-UM).    The  organ  by  which  ova  are  produced. 

O-VIP'A-ROUS  (Lat.  ovum,  an  egg  ;  and  pario,  I  bring  forth).  Applied  to  ani- 
mals which  bring  forth  eggs,  in  contradistinction  to  those  which  bring  forth 
their  young  alive. 

O-VI-POS'I-TOR  (Lat.  ovum;  andpono,  I  place).  The  organ  possessed  by 
some  insects,  by  means  of  which  the  eggs  are  placed  in  a  position  suitable 
for  their  development. 

O'vi-SAO.  The  external  bag  or  sac  in  which  certain  of  the  Invertebrates 
carry  their  eggs  after  they  are  extruded  from  the  body. 


342  GLOSSARY. 

O-VO-VI-VIP'A-ROTTS  (Lat.  ovum,  egg ;  vivus,  alive ;  pario,  I  pro  luce).  Ap- 
plied to  animals  which  retain  their  eggs  within  the  body  until  they  are 

O'VUM  (Lat.  for  an  egg).  The  germ  produced  within  the  ovary,  and  capable 
under  certain  conditions  of  being  developed  into  a  new  individual. 

PACH-Y-DER'MA-TA  (Gr.  pachus,  thick ;  derma,  skin).  An  old  Mammalian 
order  constituted  by  Cuvier  for  the  reception  of  the  Khinoceros,  Hippopota- 
mus, Elephant,  etc. 

PA-L.E-ON-TOI/O-GY  (Gr. palaios,  ancient-  onta,  beings;  and  logos,  discourse). 
The  science  of  fossil  remains  or  of  extinct  organized  beings. 

PA-L.E-O-ZO'IO  (Gr.  palaios,  ancient ;  and  zoe,  life).  Applied  to  the  oldest  of 
the  great  geological  epochs. 

PAL'LI-AL. 

PAL-LI-O-BRA^-CHI-A'TA  (Lat.  pallium  ;  and  Gr.  bragchia,  gills).  An  old  name 
for  the  Brachiopoda,  founded  upon  the  belief  that  the  system  of  tubes  in 
the  mantle  constituted  the  gills. 

PAL'LI-UM  (Lat.  pallium,  a  cloak).  The  mantle  of  the  Mollusca.  Pallial : 
relating  to  the  mantle.  Pallial  line  or  impression  :  the  line  left  in  the  dead 
shell  by  the  muscular  margin  of  the  mantle.  Pallial  shell :  a  shell  which 
is  secreted  by,  or  contained  within,  the  mantle,  such  as  the  "  bone  "  of  the 
Cuttle-fishes. 

PAL'PI  (Lat.  palpo,  I  touch).  Processes  supposed  to  be  organs  of  touch,  de- 
veloped from  certain  of  the  oral  appendages  in  Insects,  Spiders,  and  Crus- 
tacea, and  from  the  sides  of  the  mouth  in  the  Acephalous  Molluscs. 

PA-PIL'LA  (Lat.  for  nipple).     A  minute  soft  prominence. 

PAR-A-PO'DI-A  (Gr.  para,  beside  ;  podes,  feet).  The  unarticulated  lateral  loco- 
motive processes  or  "foot-tubercles"  of  many  of  the  Annelida. 

PA-RI'E-TAL  (Lat.  paries,  a  wall).  Connected  with  the  walls  of  a  cavity  or  of 
the  body. 

PA-Ri-E-To-spLANCH'iac  (Lat.  paries;  Gr.  splagchna,  viscera).  Applied  to 
one  of  the  nervous  ganglia  of  the  Mollusca,  which  supplies  the  walls  of  the 
body  and  the  viscera. 

PAR-THEN-O-GEN'E-SIS  (Gr.  parthenos,  a  virgin  ;  and  genesis,  production). 
Strictly  speaking,  confined  to  the  production  of  new  individuals  from  virgin 
females  by  means  of  ova  without  the  intervention  of  a  male.  Sometimes 
used  also  to  designate  a  sexual  reproduction  by  gemmation  or  fission. 

PAT-A-GI'UM  (Lat.  for  the  border  of  a  dress).  Applied  to  the  expansion  of  the 
integument  by  which  Bats,  Flying  Squirrels,  and  other  animals  support 
themselves  in  the  air. 

PA-TEI/LA  (Lat.  for  the  knee-cap  or  knee-pan).  A  sesamoid  bone  devel- 
oped in  the  tendon  of  insertion  of  the  great  extensor  muscles  of  the  thigh. 

PEC'TI-NATE  (Lat.  pecten,  a  comb).  Comb-like ;  applied  to  the  gills  of  certain 
Gasteropods,  hence  called  Pectinibranchiata. 

PEC'TO-RAL  (Lat.  pectus,  chest).     Connected  with,  or  placed  upon,  the  chest. 

PE'DAL  (Lat.  pes,  the  foot).    Connected  with  the  foot  of  Mollusca. 

PED-I-CEL-LA  RI-.E  (Lat.  pedicellus,  a  louse).  Certain  singular  appendages 
found  in  many  Echinoaerms,  attached  to  the  surface  of  tne  body,  and  re- 
sembling a  little  beak  or  forceps  supported  on  a  stalk. 

PED'I-CLE  (Lat.  dimin.  of  pes,  the  foot).    A  little  stem. 

PED-I-PAL'PI  (Lat.  pes,  foot ;  and  palpo,  I  feel).  An  order  of  Arachnida 
comprising  the  Scorpions,  etc. 

PE-DUN'CLE  ^Lat.  pedunculus,  a  stem  or  stalk).  In  a  restricted  sense  applied 
to  the  muscular  process  by  which  certain  Brachiopods  are  attached,  and  to 
the  stem  which  bears  the  body  (capitulum)  in  Barnacles. 

PE-DUN'CU-LATE.    Possessing  a  peduncle. 

PE-DUN'CU-LA-TED. 

PE-LAO'IO  (Gr.  pelagos,  sea).    Inhabiting  the  open  ocean. 

PEI/VIS  (Lat.  for  basin).  Applied,  from  analogy,  to  the  basal  portion  of  the 
cup  (calyx)  of  Cr^no^ds.  Tne  body  arch  with,  which  the  hind-limbs  are 
connected  in  Vertebrates. 


GLOSSARY.  343 

PER-EN-NI-BRAN-CHI-A'TA  (Lat.  perennis,  perpetual ;  Gr.  bragchia,  gills).  Ap- 
plied to  those  Amphibia  in  which  the  gills  are  permanently  retained  through- 
out life. 

PER-GA-MEN-TA'CEOTJS  (Lat.  pergamena,  parchment).  Of  the  texture  of  parch- 
ment. 

PER-I-CAR'DI-TTM  (Gr.  peri,  around ;  Icardia,  heart).  The  serous  membrane  in 
which  the  heart  is  contained. 

PER'I-DERM  (Gr.  peri,  around  ;  and  derma,  skin).  The  hard  cuticular  layer 
which  is  developed  by  the  crenosarc  of  certain  of  the  Uydrozoa. 

PER-I-GAS'TRIC  (Gr.  peri,  around  :  and  gaster,  stomach).  The  perigastric  space 
is  the  cavity  which  surrounds  the  stomach  and  other  viscera,  corresponding 
to  the  abdominal  cavity  of  the  higher  animals. 

PER-I-OS'TRA-CUM  (Gr.  peri;  and  ostrakon,  shell).  The  layer  of  epidermis 
which  covers  the  shell  in  most  of  the  Mollusca. 

PER'I-PLAST  (Gr.  peri;  and  p^lasso,  I  mould).  The  intercellular  substance  or 
matrix  in  which  the  organized  structures  of  a  tissue  are  embedded. 

PER'I-SOME  (Gr.peri  ;  ancUoma, body).  The  coriaceous  or  calcareous  integu- 
ment of  the  Echinodermata. 

PER-IS-SO-DAC'TY-LA  (Gr.perissos,  uneven ;  daktulos,  finger).  Applied  to  those 
Hoofed  Quadrupeds  ( Ungulata)  in  which  the  feet  have  an  uneven  number 
of  toes. 

PER'I-STOME  (Gr.  peri;  and  stoma,  mouth).  The  space  which  intervenes  be- 
tween the  mouth  and  the  margin  of  the  calyx  in  Vorticdla  ;  also  the  space 
between  the  mouth  and  the  tentacles  in  a  sea-anemone  (Actinia) ;  also  the 
lip  or  margin  of  the  mouth  of  a  univalve  shell. 

PER-I-VIS'CE-RAL  (Gr.  peri;  and  Lat.  viscera,  the  internal  organs).  Applied 
to  the  space  surrounding  the  viscera. 

PET'A-LOID.     Shaped  like  the  petal  of  a  flower. 

PHA-LAN'GES  (Gr.  phalagx,  a  row).  The  small  bones  composing  the  digits  of 
the  higher  Vertebrata.  Normally  each  digit  has  three  phalanges. 

PIIAR-YN-GO-BRAN'CHI-I  (Gr.  vharugx,  pharynx ;  bragch^a,  gills).  The  order 
of  Fishes  comprising  only  the  Lancelet. 

PHAR'YNX.     The  dilated  commencement  of  the  gullet. 

PHRAG'MA-CONE  (Gr.  phragma,  a  partition  •  and  konos,  a  cone).  The  cham- 
bered portion  of  the  internal  shell  of  a  Belemnite. 

PH  Y-LAC-To-L.fi  M'A-T- A  (Gr.  phulasso,  I  guard ;  and  laimos,  throat).  The  divi- 
sion of  Polyzoa  in  which  the  mouth  is  provided  with  the  arched  valvular 
yjrocess  known  as  the  "  epistome." 

PHYL'LO-CYSTS  (Gr.  phullon,  leaf;  undkustis,  a  cyst).  The  cavities  in  the  in- 
terior of  the  "  hydrophyllia  "  of  certain  of  the  Oceanic  Hydrozoa. 

PHYL-LOP'O-DA  (Gr.  phullon,  leaf ;  and pous,  foot).    An  order  of  Crustacea. 

PHY-O-GEM-MA'RI-A  ( (Jr.  pkuo,  I  produce  ;  and  Lat.  gemma,  bud).  The  small 
gonoblastidia  of  Velella,  one  of  the  Physophwidce. 

PHY-SO-GRA'DA  (Gr.  phusa,  bellows  or  air-bladder  ;  and  Lat.  gradior,  I  walk). 
Applied  formerly  to  the  Physophoridoe,  an  order  of  Oceanic  Hydrozoa,  in 
which  a  "  float "  is  present. 

PHY-SO-PHOR'I-D^:  (Gr.  phusa,  air-bladder ;  audphero,  I  carry).  An  order  of 
Oceanic  Hydrozoa. 

PHY'TOID  (Gr.  pJiuton,  a  plant ;  and  eidos,  form).    Plant-like. 

PHY-TOPH'A-SOUS  (Gr.  ptiuton,  a  plant ;  and  phago^  I  eat).  Plant-eating,  or 
herbivorous. 

PIN'N^E. 

PIN'NATE  (Lat.  pinna,  a  feather).  Feather-shaped,  or  possessing  lateral  pro- 
cesses. 

PIN-NI-GRA'DA  (Lat. pinna,  a  feather:  qradior,  I  walk).  The  group  of  Car- 
nivora,  comprising  the  Seals  and  Walruses,  adapted  for  aquatic  lire.  Often 
called  Pinmpedia. 

PIN'NC-LJS  (Lat.  dim.  of  pinna.)  The  lateral  processes  of  the  arms  of  Ori- 
noids. 

PIS'CES  (Lat.  piscis,  a  fish).     The  class  of  Vertebrates  comprising  the  Fishes. 

PIA-CEN'TA  (Lat.  for  a  cake.)    The  "  after-birth,"  or  the  organ  by  which  a 


344  GLOSSARY. 

vascular  connection  is  established  in  the  higher  Mammalia  between  the 

mother  and  the  foetus. 

PLA-CEN'TAL.    Possessing  a  placenta,  or  connected  with  the  placenta. 
PLAC'OID  (Gr.  plax,  a  plate  ;  eidos,  form).     Applied  'to  the  irregular  bony 

plates,  grains,  or  spines,  which  are  found  in  the  skin  of  various  fishes 

(MasmobrancMi). 
PLA-GI-OS'TO-MI  (Gr.  plagios,  transverse ;  stoma,  mouth).    The  Sharks  and 

Rays,  in  which  the  mouth  is  transverse,  and  is  placed  on  the  under  surface 

of  the  head. 

PLA-NAB'I-DA  (Gr.  plane,  wandering).    A  sub-order  of  the  TurbeUaria. 
PLAN-TI-GBA'DA. 
PLANT' I-GBADE  (Lat.  planta,  the  sole  of  the  foot ;  gradior,  I  walk).    Applying 

the  sole  of  the  foot  to  the  ground  in  walking. 
PLAN'U-LA  (Lat.  planus,  flat).    The  oval  ciliated  embryo  of  certain  of  the  Hy- 

drozoa. 

PLAS'TRON.    The  lower  or  ventral  portion  of  the  bony  case  of  the  Chelonians. 
PLAT-Y-EL'MI-A  (Gr.  platus,  broad ;   and  kelmins,  an  intestinal  worm).     The 

division  of  Scolecida  comprising  the  Tape- worms,  etc. 
PLAT-Y-RHI'NA  (Gr.  platus,  broad  ;  rhines,  nostrils).    A  group  of  the  Quadru- 

mana. 

PLE-SI-O-SAU'ETTS  (Gr.  plesios,  near  to  ;  and  savxrus,  lizard). 
PLEU'BA  (Gr.  for  the  side).    The  serous  membrane  covering  the  lung  hi  the 

air-breathing  Vertebrates. 

PLEU'BON  (Gr.  pleuron,  a  rib).  The  lateral  extensions  of  the  shell  of  Crustacea. 
PLU'TE-US  (Lat.  for  a  pent-house).    The  larval  form  of  the  EcHnoidea. 
PNEU-MAT'IC  (Gr.  pneuma,  air).     Filled  with  air. 
PNEU-MAT'O-CYST  (Gr.  pneuma,  air;  and  Icustis,  cyst).     The  air-sac  or  float  of 

certain  of  the  Oceanic  Hydrozoa  (Physophoridce). 

PNEU-MAT'O-PHOBE  (Gr.  pneuma,  air ;  andphero,  I  carry).  The  proximal  dilata- 
tion of  the  ccenosarc  in  the  Physophoridce  which  surrounds  the  pneumatocyst. 
PNEU-MO-SKEI/E-TON  (Gr.  pneuma,'    and  sTceletos,  dry).     The  hard  structures 

which  are  connected  with  the  breathing  organs  (e.  g.,  the  shell  of  Molluscs). 
POD-OPH-THAL'MATA  (Gr.  pous,  foot;  and  ophthalmos,  eye).     The  division  of 

Crustacea  in  which  the  eves  are  borne  at  the  end  of  long  foot-stalks. 
POD-O-SOM'A-TA  (Gr.  pous,  foot :  soma,  body).    An  order  of  Arachnida. 
PO-EPH'A-GA  (Qi.poe,  grass ;  phago,  I  eat).    A  group  of  the  Marsupials. 
POIS'EBS. 
POL'LEX  (Lat.  for  the  thumb).    The  innermost  of  the  five  normal  digits  of  the 

anterior  limb  of  the  higher  Vertebrates.     In  man,  the  thumb. 
POL-Y-CYS-TI'NA  (Gr.  polus,  many ;  and  Tcustis,  a  cyst).   An  order  of  Protozoa, 

with  foraminated  siliceous  shells. 
PO-LYG'A-MOUS  (Gr.  polus  ;  and  gamos,  marriage). 
POL-Y-GAS'TEI-CA  (Gr.  polus ;  and  gaster,  stomach).     The  name  applied  by 

Ehrenberg  to  the  Infusoria,  under  the  belief  that  they  possessed  many 

stomachs. 

POL'Y-PA-BY  (Gr.  polus;  and  pario,  I  produce).    The  hard  chitinous  cover- 
ing secreted  by  many  of  the  Hydrozoa. 
POL'YPE  (Gr.  polus,  many ;  pous,  foot).    ^Restricted  to  the  single  individual 

of  a  simple  Actinozoon,  such  as  a  Sea-anemone,  or  to  the  separate  zooids  of 

a  compound  Actinozoon.     Often  applied  indiscriminately  to  any  of  the 

Codenterata,QT:  even  to  the  Polyzoa. 
POI/Y-PIDE.    The  separate  zooid  of  a  Polyzoon. 

POL-YP'I-DOM.    The  dermal  system  of  a  colony  of  a  Eydrozoon,  or  Polyzo'un. 
POL'Y-PITE.    The  separate  zooid  of  a  Hydrozoon. 
POI/Y-STOME  (Gr.  polus,  many ;  and  stoma,  mouth).    Having  many  mouths  ; 

applied  to  the  Acinetce  among  the  Protozoa. 
POL-Y-THAL'A-MOUS  (Gr.  polus;   and  thalamos.  chamber).      Having  many 

chambers  ;  applied  to  the  shells  of  Foraminifera  and  Cephalopoda. 
POL-Y-ZO'A  (Gr.  polus;  and  zo'on,  animal).    A  division  oi  the  Molluscoida. 

comprising  compound  animals,  such  as  the  Sea-mat.    Sometimes  called 


GLOSSARY.  345 

POL-Y-ZO-A'RI-UM.  The  dermal  system  of  the  colony  of  a  Polyzoon  (=  Polypi- 
dom). 

POR-CEL-LA'NE-OUS.     Of  the  texture  of  porcelain. 

PO-RIF'E-RA  (Lat.  porus,  a  pore ;  and /era,  I  carry.  Sometimes  used  to  desig- 
nate the  Forarmnifera,  or  the  Sponges. 

POST'A-NAL  (Lat.  post,  behind ;  amis,  the  fundament).  Situated  behind  the 
anus. 

POST-OE-SO-PHAG'E-AL  (Gr.  oisophagos,  the  gullet).    Situated  behind  the  gullet. 

POST-O'RAL  (Lat.  os,  mouth).     Situated  behind  the  mouth. 

PR.E-MAX-IL  L,E.     (See  Intennaxillae.) 

PR^E-MO'LARS  (Lat.  prae,  before ;  molares,  the  grinders).  The  molar  teeth  of 
Mammals  which  succeed  the  molars  of  the  milk-set  of  teeth.  In  man,  the 
bicuspid  teeth. 

PR.E-(E-SO-PHAG'E-AL.    Situated  in  front  of  the  gullet. 

PR^E-STER'NUM  (Gr.  sternon,  the  breast).  The  anterior  portion  of  the  breast- 
bone, corresponding  with  the  manubrium  sterni  of  nunian  anatomy,  and 
extending  as  far  as  the  point  of  articulation  of  the  second  rib. 

PREs-si-RoaTRES  (Lat.  presses,  compressed ;  rostrum,  beak).  A  group  of  the 
Grallatorial  Birds. 

PROB-OS-CID'E-A  (Lat.  prob  scis,  the  snout).  The  order  of  Mammals  com- 
prising the  Elephants. 

PRO-BOS  cis  (Lat.  or  Gr.  for  the  snout).  Applied  to  the  spiral  trunk  of  Lepidop- 
terous  Insects,  to  the  projecting  mouth  of  certain  Crinoids,  and  to  the  cen- 
tral polypite  in  the  Medusa. 

PRO-CCE'LOUS  (Gr. pro,  in  front;  Icoilos,  hollow).  Applied  to  vertebrae,  the 
bodies  of  which  are  hollow  or  concave  in  front. 

PRO-GLOT'TIS  (Gr.  for  the  tip  of  the  tongue).  The  generative  segment  or  joint 
of  a  Tape-worm. 

PRO'LEGS.    The  false  abdominal  feet  of  Caterpillars. 

PRO-NA'TION  (Lat.  pronus,  lying  on  the  face,  prone).  The  act  of  turning  the 
palm  of  the  hand  downward. 

PRO-PO'DI-UM  (Gr.  pro,  before ;  pous,  foot).  The  anterior  part  of  the  foot  in 
Molluscs. 

PRO-SCO'LEX  (Gr.  pro,  before ;  scolex,  worm).  The  first  embryonic  stage  of  a 
Tape-worm. 

PROS-O-BRAN-CHI-A'TA  (Gr.  proso,  in  advance  of;  Iragchia,  gills).  A  division 
of  Gasteropodous  Molluscs  in  which  the  gills  are  situated"  in  advance  of  the 
heart. 

PRO-SO'MA  (Gr.  pro,  before ;  soma,  body).    The  anterior  part  of  the  body. 

PRO-THO'RAX  ^Gr.  pro ;  and  t7torax,  chest).  The  anterior  ring  of  the  thorax 
of  insects. 

PRO-TOPH'Y-TA  (Gr.  protos,  first ;  andphuton,  plant).     The  lowest  division  of 

'    plants. 

PRO'TO-PLASM  (Gr.  protos ;  and  plasso,  I  mould).  The  elementary  basis  of 
organized  tissues.  Sometimes  used  synonymously  for  the  "sarcode"  of 
the  Protozoa. 

PRO-TOP'O-DITE  (Gr. protos/  and  pous,  foot).  The  basal  segment  of  the  typi- 
cal limb  of  a  Crustacean. 

PRO-TO-ZO'A  (Gr.  protos ;  and  zoZn,  animal).  The  lowest  division  of  the  ani- 
mal kingdom. 

PRO-VEN-TRIC'U-LL'S  (Lat.  pro,  in  front  of;  ventriculus,  dim.  of  venter,  belly). 
The  cardiac  portion  of  the  stomach  of  Birds. 

PROX'I-MAL  (Lat.  proximus,  next).  The  slowly-growing,  comparatively-fixed 
extremity  of  a  limb  or  of  an  organism. 

PSAL-TE'RI-UM  (Lat.  for  a  stringed  instrument).  The  third  stomach  of  Ku- 
minants.  (See  Omasum.) 

PSEC-DEM'BRY-O  (Gr.  pseudes,  false ;  emlruon,  embryo).  The  larval  form  of 
an  Echinoderm. 

PSSU-DO-BRAN'CHI-A  (Gr.  pseudes,  false  ;  bragchia,  gills).  A  supplementary  gill 
found  in  certain  fishes,  which  receives  arterialized  blood  only,  and  does 
not,  therefore,  assist  in  respiration. 


346  GLOSSARY. 

PSEU-DO-H.E'MAL  (Gr.  pseudes,  false  ;  and  Tiaima,  blood).  Applied  to  the 
vascular  system  of  Annelida. 

PSEU'DO-HEABTS.  Certain  contractile  cavities  connected  with  the  atrial  sys- 
tem of  Brachiopoda,  and  long  considered  to  be  hearts. 

PSEU-DO-NAV-I-CEL'L^E  ( Gr.  pseudes,  false  ;  and  Navicula,  a  genus  of  Diatoms). 
The  embryonic  forms  of  the  Grcgarinidce,  so  called  from  their  resemblance 
in  shape  to  the  Navicula. 

PSEU-DO-PO'DI-A  (Gr.  pseudes  ;  and  pous,  foot).  The  extensions  of  the  body- 
substance  which  are  put  forth  by  the  Rhizopoda  at  will,  and  which  serve 
for  locomotion  and  prehension. 

PSEU-DO'VA  (Gr.  pseudes  ;  (Lat.  ovum,  egg).  The  egg-like  bodies  from  which 
the  young  of  the  viviparous  Aphis  are  produced. 

PTEE-OP'O-DA  (Gr.  pteron,  wing ;  and  pous,  foot).  A  class  of  the  Mollusca 
which  swim  by  means  of  fins  attached  near  the  head. 

PTEB-O-SAU'BI-A  (Gr.  pteron,  wing  ;  saura,  lizard).  An  extinct  order  of  Bep- 
tiies. 

PU'BIS  (Lat.  pubes,  hair).  The  share-bone ;  one  of  the  bones  which  enter 
into  the  composition  of  the  pelvic  arch  of  Vertebrates. 

PUL-MO-GAS-TEB-OP'O-DA  (=  Pulmonifera). 

PUL-MO-NA'BI-A.  A  division  of  Arachnida  which  breathe  by  means  of  pulmo- 
nary sacs. 

PUL'MO-NA-BY. 

PUL'MO-NATE.    Possessing  lungs. 

PUIXHO-NIF'E-BA  (Lat.  pulmo,  a  lung ;  and  fero,  I  carry).  The  division  of 
Mollusca  which  breathe  by  means  of  a  pulmonary  chamber. 

PU'PA  (Lat.  for  a  doll).  The  stage  of  an  insect  immediately  preceding  its  ap- 
pearance in  a  perfect  condition.  In  the  pupa-stage  it  is  usually  quiescemV- 
when  it  is  often  called  a  "  chrysalis ; "  but  it  is  sometimes  active— when  it 
is  often  called  a  "  nymph." 

PY-LO'EUS  (Gr.  puloros,  a  gatekeeper).  The  valvular  aperture  between  the 
stomach  and  the  intestines. 

PYB'I-FOBM  (Lat.  pirum  orpyrum,  a  pear;  and  forma,  form).    Pear-shaped. 

QUAD-BTT-MA'NA  (Lat.  quatuor,  four:  manus,  hand).  The  order  of  Mammals 
comprising  the  Apes,  Monkeys,  Baboons,  Lemurs,  etc. 

QUAD-BU-MA  NOUS. 

EA-DI-A'TA  (Lat.  radius,  a  ray).  Formerly  applied  to  a  large  number  of  ani- 
mals which  are  now placed*in  separate  sub-kingdoms  (e.  g.,  the  C&lenierata, 
the  Echinodermata,  the  Infusoria,  etc.). 

BA-DI-O-LA'BI-A  (Lat.  radius,  a  ray).    A  division  of  Protozoa. 

KA'DI-US  (Lat.  for  a  spoke  or  ray).  The  innermost  of  the  two  bones  of  the  fore- 
arm of  the  higher  Vertebrates.  It  carries  the  thumb,  when  present,  and 
corresponds  with  the  tibia  of  the  hind-limb. 

BA'MUS  (Lat.  for  a  branch).  Applied  to  each  half  or  branch  of  the  lower  jaw 
or  mandible  of  Vertebrates. 

EAP-TO'BES  (Lat.  rapio,  I  plunder).    The  order  of  the  birds  of  Prey. 

EAP-TO'BI-AL. 

BA-SO'BES  (Lat.  rado,  I  scratch).  The  order  of  the  Scratching  Birds  (Fowls, 
Pigeons,  etc.). 

EA-TI'T^:  (Lat.  ratis,  a  raft).  Applied  by  Huxley  to  the  Cursorial  Biids,  which 
do  not  fly,  and  have  therefore  a  raft-like  sternum  without  any  median  keel. 

EEC'TUM  (Lat.  rectus,  straight).  The  terminal  portion  of  the  intestinal  canal, 
opening  at  the  surface  of  the  body  at  the  anus. 

Bfip-Tii/i-A  (Lat.  repo,  I  crawl).  The  class  of  the  Vertebrata  comprising  tho 
Tortoises.  Snakes,  Lizards,  Crocodiles,  etc. 

RE-TIC-U-LA  BI-A  (Lat.  reticulum,  a  net).  Employed  by  Dr.  Carpenter  to  desig- 
nate those  Protozoa,  such  as  the  Foraminifera,  in  which  the  pseudopodia 
run  into  one  another  and  form  a  network. 

BE-TIO'U-LTJM  (Lat.  for  a  net).  The  second  division  of  the  complex  stomach 
of  Buminants,  often  called  the  "  honey-couib  bag." 


GLOSSARY.  347 

RE-VERSED'.  Applied  to  spiral  univalves,  in  which  the  direction  of  the  spiral 
is  the  reverse  of  the  normal — i.  e.,  sinistral. 

RHI-ZOPH'A-GA  (Gr.  rhiza,  root ;  pltago,  I  eat).    A  group  of  the  Marsupials. 

RHI-ZOP'O-DA  (Gr.  rhiza,  a  root;  and  pous,  foot).  Trie  division  of  Protozoa 
comprising  all  those  which  are  capable  of  emitting  pseudopodia. 

RHTN'CHO-LITES  (Gr.  rhugchos,  beak;  and  lithos,  stone).  Beak-shaped  fos- 
sils, consisting  of  the  mandibles  of  Cephalopoda. 

RO-DEN'TI-A  (Lat.  rodo,  I  gnaw).  An  order  of  the  Mammals ;  often  called 
Glires  (Lat.  glis,  a  dormouse). 

ROS'TRUM  (Lat.  rostrum,  beak).  The  "beak"  or  suctorial  organ  formed  by 
the  appendages  of  the  mouth  in  certain  insects. 

RO-TA-TO  RI-A  (=  Rotifera). 

RO-TIF'E-RA  (Lat.  rota,  wheel ;  and  fero,  I  carry  \  A  class  of  the  Scolecida 
(Annuloida)  characterized  by  a  ciliated  "  trocnal  disc." 

RU-GO'SA  (Lat.  rugosus,  wrinkled ).    An  extinct  order  of  Corals, 

RU'MEN  (Lat.  for  the  throat).  The  first  cavity  of  the  complex  stomach  of  Ru- 
minants ;  often  called  the  "  paunch." 

RU-MI-NAN'TI-A  (Lat.  ruminor,  I  chew  the  cud).  The  group  of  Hoofed  Quad- 
rupeds (  Ungulata)  which  "  ruminate  "  or  chew  the  cud. 

SA'CRUM.  The  vertebrae  (usually  anchylosed)  which  unite  with  the  haunch- 
bones  (ilia)  to  form  the  pelvis. 

SAND-CA-NAL  (=  STONE-CA-NAL).  The  tube  by  which  water  is  conveyed  from 
the  exterior  to  the  ambulacral  system  of  the  Echinodermata. 

SAR'CODE  (Gr.  sarx,  flesh ;  eidos,  form).  The  jelly-like  substance  of  which 
the  bodies  of  Protozoa  are  composed.  It  is  an  albuminous  body  containing 
oil-granules,  and  is  sometimes  called  "  animal  protoplasm." 

SAR'COIDS  (Gr.  sarx;  and  eidos,  form).  The  separate  amoebiform  particles 
which  in  the  aggregate  make  up  the  "flesh"  of  a  Sponge. 

SATJ'EI-A  (Gr.  saura,  a  lizard).  _  Any  lizard-like  Reptile  is  often  spoken  of  as 
a  "  Saurian ; "  but  the  term  is  sometimes  restricted  to  the  Crocodiles  alone, 
or  to  the  Crocodiles  and  Lacertilians. 

SAU-RO-BA-TRA'CHI-A  (Gr.  saura  ;  batraehos,  frog).  Sometimes  applied  to  the 
order  of  the  tailed  Amphibians  (  Urodela). 

SAU-ROP'SI-DA  (Gr.  saura  ;  andopsis,  appearance).  The  name  given  by  Hux- 
ley to  the  two  classes  of  the  Birds  and  Reptiles  collectively. 

SAU-ROP-TER-YG'I-A  (Gr.  saura;  andpterux,  wing).  An  extinct  order  of  Rep- 
tiles, called  by  Huxley  Plesiosauria.  from  the  typical  genus  Plesiosaurus. 

SAU-RU'R^:  (Gr.  saura  ;  and  oura,  tail).  The  extinct  order  of  Birds  compris- 
ing only  the  Archceopteryx.  ^ 

SCAN-SO'RES  (Lat.  scando,  I  climb).  The  order  of  the  Climbing  Birds  (Par- 
rots, Woodpeckers,  etc.). 

SCA-PHOO'NA-THITE  (Gr.  skapJios,  boat ;  and  gnaihos,  jaw).  The  boat-shaped 
appendage  (epipodite)  of  the  second  pair  of  maxillae  in  the  Lobster ;  the 
function  of  which  is  to  spoon  out  the  water  from  the  branchial  chamber. 

SCAP'U-LA  (Lat.  for  shoulder-blade).  The  shoulder-blade  of  the  pectoral  arch 
of  Vertebrates :  in  a  restricted  sense,  the  row  of  plates  in  the  cup  of  Ori- 
noids,  which  give  origin  to  the  arms,  and  are  usually  called  the  "axillary 
radials." 

SOLE-REN'CHY-MA  (Gr.  skleros,  hard  ;  and  egchuma,  tissue).  The  calcareous 
tissue  of  which  a  coral  is  composed.. 

SCLE'RITES  (Gr.  skleros).  The  calcareous  spicules  which  are  scattered  in  the 
soft  tissues  of  certain  Actinozoa. 

SOLER-O-BA'SIO  (Gr.  skleros,  hard ;  Jam,  pedestal).  The  coral  which  is  pro- 
duced by  the  outer  surface  of  the  integument  in  certain  Actinozoa  (e,  g., 
Red  Coral),  and  forms  a  solid  axis  which  is  invested  by  the  soft  parts  of  the 
animal.  It  is  called  "  foot-secretion"  by  Mr.  Dana. 

SOLER-O-DER'MIO  (Gr.  skleros ;  and  derma,  skin).  Applied  to  the  corallum 
which  is  deposited  within  the  tissues  of  certain  Actmozoa,  and  is  called 
"tissue-secretion"  by  Mr.  Dana. 

SOLE-BOT'IO  (Gr.  sUeros,  hard).    The  outer  dense  fibrous  coat  of  the  eye. 


348  GLOSSARY. 

SCO-LEC'I-DA  (Gr.  skolex,  worm).     A  division  of  the  Annuloida. 

SCO'LEX  (Gr.  for  worm).  The  embryonic  stage  of  a  Tape-worm,  formerly 
known  as  a  "  Cystic  Worm." 

SOU'TA  (Lat.  scutum,  a  shield).  Applied  to  any  shield-like  plates  ;  especially 
to  those  which  are  developed  in  the  integument  of  many  Keptiles. 

SE-LA'CHI-A  or  SE-LA'CHI-I  (Gr.  selachos,  a  cartilaginous  fish,  probably  a  shark). 
The  sub-order  of  Elasmobranchii,  comprising  the  Sharks  and  Dog-fishes. 

SE'PI-O-STAIRE  (Lat.  and  Gr.  sepia,  the  cuttle-fish.)  The  internal  shell  of  the 
Cuttle-fish,  commonly  known  as  the  "  cuttle-bone." 

SEP'TA.     Partitions. 

SER-PEN'TI-FORM.    Resembling  a  serpent  in  shape. 

SER-TU-LAR'I-DA  (Lat.  sertum,  a  wreath).     An  order  of  Hydrozoa. 

SES'SILE  (Lat.  sedeo,  I  sit).  Not  supported  upon  a  stalk  or  peduncle  ;  attached 
by  a  base. 

SE'TJS  (Lat.  for  bristles).    Bristles,  or  long  stiff  hairs. 

SE-TIF'ER-OUS.    Supporting  bristles. 

SE-TIG'ER-OUS  (=  Setiferous). 

SE'TOSE.    Bristly. 

SI-LIC'EOUS  (Lat.  silex,  flint).     Composed  of  flint. 

SIN'IS-TRAL  (Lat.  sinutra,  the^left  hand).  _  Left-handed ;  applied  to  the  di- 
rection of  the  spiral  in  certain  shells,  which  are  said  to  be  reversed." 

SI'NCS  (Lat.  sinus,  a  bay).     A  dilated  vein  or  blood-receptacle. 

SI'PHOIT  (Gr.  siphon,  a  tube).  Applied  to  the  respiratory  tubes  in  the  Mol- 
lusca  /  also  to  other  tubes  of  different  functions. 

SI-PHON-OPH'O-RA  (Gr.  siphon;  &ndphero,  I  carry).  A  division  of  the  Hydro- 
zoo,,  comprising  the  Oceanic  forms  ( Galycophoridm  and  Physophoridce). 

SI-PHON-O-STOM'A-TA  (Gr.  siphon  ;  and  stoma,  mouth).  The  division  of  G-aster- 
opodous  Molluscs,  in  which  the  aperture  of  the  shell  is  not  "  entire,"  but 
possesses  a  notch  or  tube  for  the  emission  of  the  respiratory  siphon. 

SI-PHUN'CLE  (Lat.  siphunculus,  a  little  tube).  The  tune  which  connects  to- 
gether the  various  chambers  of  the  shell  of  certain  Cephalopoda  (e.  g.,  the 
Pearly  Nautilus). 

SI-PHCN-CU-LOI'DE-A  (Lat.  siphunculus,  a  little  siphon).  A  class  of  Anarthrop- 
oda  (Annulosa). 

SI-RE'NI-A  (Gr.  seiren,  a  mermaid).  The  order  of  Mammalia  comprising  the 
Dugongs  and  Manatees. 

SOJ>ID-UN'OU-LA  (Lat.  solidus,  solid ;  ungula,  a  hoof).  The  group  of  Hoofed 
Quadrupeds  comprising  the  Horse,  Ass,  and  Zebra,  in  which  each  foot  has 
only  a  single  solid  hoof.  Often  called  Solipedia. 

SO-MAT'IO  (Gr.  soma,  body).     Connected  with  the  body. 

SO-MAT'O-CYST  (Gr.  soma  ;  and  Icustis,  a  cyst).  A  peculiar  cavity  in  the  cceno- 
sarc  of  the  Calycophorida  (Hydrozoa). 

SO'MITE  (Gr.  soma}.    A  single  segment  in  the  body  of  an  Articulate  animal. 

SPER-MA  RI-TJM.    The  organ  in  which  spermatozoa  are  produced. 

SPER-MAT'O-PHORES  (Gr.  sperma,  seed ;  phero,  I  carry).  The  cylindrical  cap- 
sules of  the  Cephalopoda,  which  carry  the  spermatozoa ;  sometimes  called 
the  "  moving  filaments  of  Needham." 

SPER-JIA-TO-ZO  A  (Gr.  sperma,  seed ;  and  zoon,  animal).  The  microscopic  fila- 
ments which  form  the  essential  generative  element  of  the  male. 

SPI'CU-LA  (Lat.  spiculum,  a  point).    Pointed  needle-shaped  bodies. 

SPIN'NER-ETS.  The  organs  by  means  of  which  Spiders  and  Caterpillars  spin 
threads. 

SPI'RA-CLES  (Lat.  spiro,  I  breathe).  The  breathing-pores,  or  apertures  of  the 
breathing-tubes  (tracheae)  of  Insects.  Also  the  single  nostril  of  the  Hag- 
fishes,  the  "  blow-hole  "  of  Cetaceans,  etc. 

SPLANOH-STO-SKEI/E-TON  (Gr.  splagchna,  viscera  ;  skeletos,  dry).  The  hard 
structures  occasionally  developed  in  connection  with  the  internal  organs  or 
viscera. 

SPONGE-PAR'TI-CLES.     (See  Sarcoids). 

SPON'GI-DA  (Gr.  spoggos,  a  sponge).  The  division  of  Protozoa  commonly 
known  as  sponges. 


GLOSSARY.  349 

SPOKES  (Gr.  tpora,  seed).  Germs,  usually  of  plants ;  in  a  restricted  sense, 
the  reproductive  "  gemmules  "  of  certain  Sponges. 

SPO'BO-SACS  (Gr.  spora,  seed  ;  and  sakkos.  a  bag).  The  simple  generative  buds 
of  certain  Ifydrozoa,  in  which  the  medusoid  structure  is  not  developed. 

SQUA'MA-TA  (Lat.  squama,  a  scale).  The  division  of  Reptiles  comprising  the 
OpJiidia  and  Lacertilia  in  which  the  integument  develops  horny  scales,  but 
there  are  no  dermal  ossifications. 

STAT'O-BLASTS  (Gr.  statos,  stationary ;  Uastos,  bud).  Certain  reproductive  buds 
developed  in  the  interior  of  Polyzoa,  but  not  liberated  until  the  death  of 
the  parent  organ:  sm. 

STEG-AN-OPH-THAL'MA-TA  (Gr.  steganos,  covered;  and  opTithalmos,  the  eye). 
Applied  by  Edward  Forbes  to  certain  Medusce,  in  wnich  the  sense-organs 
("marginal  bodies")  are  protected  by  a  sort  of  hood.  The  SteganophthaL- 
mata  are  now  separated  from  the  true  Medusidce,  and  placed  in  a  separate 
division  under  the  name  Lucernarida. 

STEL-LEB'I-DA  (Lat.  stella,  star).  Sometimes  applied  to  designate  the  order 
of  the  Star-fishes. 

STEL'LI-FOBM.    Star-shaped. 

STEM'MA-TA  (Gr.  stemma,  garland).  The  simple  eyes,  or  "  ocelli,"  of  certain 
animals,  such  as  Insects,  Spiders,  and  Crustacea. 

STEB'NUM  (Gr.  sternon).    The  breast-bone. 

STIG'MA-TA.    The  breathing-pores  in  Insects  and  Arachnida. 

STO'LON  (Gr.  stolos,  a  sending-forth).  Off-shoots. — The  connecting  processes 
of  sarcode,  in  Foramiwifera ;  the  connecting  tube  in  the  social  Ascidians  ; 
the  processes  sent  out  by  the  coenosarc  of  certain  Actinozoa. 

STO-MAP'O-DA  (Gr.  stoma,  mouth :  pous,  foot).    An  order  of  Crustacea. 

STOM'A-TODE  (Gr.  stoma  ;  eidos,wrm).  Possessing  a  mouth.  The  Infusoria 
are  thus  often  called  the  Stomatode  Protozoa. 

STBEP-SIP'TE-BA  (Gr.  strep  ho,  I  twist ;  and  pteron,  wing).  An  order  of  In- 
sects in  which  the  anterior  wings  are  represented  by  twisted  rudiments. 

STBEPS-I-BHI'NA  (Gr.  strepho,  I  twist ;  rines,  nostrils).  A  group  of  the  Quad- 
rumana,  often  spoken  of  as  Prosi/mice. 

STBOB'I-LA  (Gr.  strobilos,  a  top,  or  fir-cone).  The  adult  Tape-worm  with  its 
generative  segments  or  proglottides ;  also  applied  to  one  of  the  stages  in 
the  life  history  of  the  Lucernarida. 

STY'LI-FOBM  (Lat.  stylus,  a  pointed  instrument ;  forma,  form).  Pointed  in 
shape. 

SUB-CAL-CA'EE-OTTS.    Somewhat  calcareous. 

SUB-CEN'TBAL.    Nearly  central,  but  not  quite. 

SUB-PE-DUN'CU-LATE.    Supported  upon  a  very  short  stem. 

SUB-SES'SILE.    Nearly  sessile,  or  without  a  stalk. 

SUO-TO'BI-AL. 

SU-PI-NA'TION  (Lat.  supinus,  lying  with  the  face  upward).  The  act  of  turn- 
ing the  hand  with  the  palm  upward. 

STJ-PBA-CE-SO-PHAG'E-AL. 

SU'TUBE  (Lat.  suo,  I  sew).  The  line  of  junction  of  two  parts  which  are  im- 
movably connected  together.  Applied  to  the  line  where  the  whorls  of  a 
univalve  shell  join  one  another ;  also  to  the  lines  made  upon  the  exterior 
of  the  shell  of  a  chambered  Cephalopod  by  the  margins  of  the  septa. 

SWIM'MEB-ETS.    The  limbs  of  Crustacea,  which  are  adapted  for  swimming. 

SYM'PHY-SIS  (Gr.  sumphusis,  a  growing  together).  Union  of  two  bones  in 
which  there  is  no  motion,  or  but  a  very  limited  amount. 

SYN-AP-TIO'U-L^:  (Gr.  sunapto,  I  fasten  together).  Transverse  props  some- 
times found  in  Corals,  extending  across  the  loculi  like  the  bars  of  a 
grate. 

SYS'TO-LE  (Gr.  sustello}  I  contract).  Applied  to  the  contraction  of  any  con- 
tractile cavity,  especially  the  heart. 

TAB'U-L.E  (Lat.  tabula,  a  tablet).    Horizontal  plates  or  floors  found  in  some 

Corals,  extending  across  the  cavity  of  the  "  theca,"  from  side  to  side. 
TAO'TILE  (Lat.  tango,  I  touch).    Connected  with  the  sense  of  touch. 
16     . 


350  GLOSSARY. 

T^E-NI'A-DA  (Gr.  tainia,  a  ribbon).  The  division  ofScoleoida  comprising  the 
Tape-worms. 

TJE'NI-OID  (Gr.  tainia /  and  eidos,  form).    Ribbon-shaped,  like  a  Tape-worm. 

TAR-SO-MET-A-TAR'SUS.  The  single  bone  in  the  leg  of  Birds  produced  by  the 
union  and  anchylosis  of  the  lower  or  distal  portion  of  the  tarsus  with  the 
whole  of  ihe  metatarsus. 

TAR'SUS  (Gr.  tarsos,  the  flat  of  the  foot).  The  small  bones  which  form  the 
ankle  (or  "  instep  "  of  man),  and  which  correspond  with  the  wrist  (carpus) 
of  the  anterior  limb. 

TEC-TI-BRAN-CHI-A'TA  (Lat.  tectus,  covered ;  and  Gr.  Iragchia,  gills).  A  divi- 
sion of  OpistJiobrancMate  Gasteropoda  in  which  the  gills  are  protected  by 
the  mantle. 

TEG-U-MENT'AR-Y  (Lat.  tegumentum,  a  covering).  Connected  with  the  integu- 
ment or  skin. 

TEL-E-OS'TE-I  (Gr.  teleios,  perfect ;  osteon,  bone).  The  order  of  the  "  Bony  " 
Fishes. 

TEL' SON  (Gr.  telson,  a  limit).  The  last  joint  in  the  abdomen  of  Crustacea; 
variously  regarded  as  a  segment  without  appendages,  or  as  an  azygos  ap- 
pendage. 

TEN-U-*-ROS'TRES  (Lat.  tennis,  slender ;  rostrum,  beak).  A  group  of  the  Perch- 
ing Birds  characterized  by  their  slender  beaks. 

TERGUM  (Lat.  for  back).    The  dorsal  arc  of  the  somite  of  an  Arthropod. 

TER-RES'TRI-AL. 

TER-RIC'O-LA  (Lat.  terra,  earth ;  and  colo,  I  inhabit).  Employed  occasionally 
to  designate  the  Earth-worms  (Lumbricidce). 

TEST  (Lat.  testa,  shell).  The  shell  of  Mollusca,  which  are  for  this  reason 
sometimes  called  "Testacea  /"  also,  the  calcareous  case  of  Echinoderma ; 
also,  the  thick,  leathery,  outer  tunic  in  the  Tunicata. 

TES-TA'CEOUS.    Provided  with  a  shell  or  hard  covering. 

TES'TIS  (Lat.  testis,  the  testicle).  The  organ  in  the  male  animal  which  pro- 
duces the  generative  fluid  or  semen. 

TET-RA-BRAN-CHI-A'TA  (Gr.  Utra,  four ;  bragchia,  gills).  The  order  of  Cephalop- 
oda, characterized  by  the  possession  of  four  gills. 

THA-LAS-SI-COL'LI-DA  (Gr.  thalassa,  sea ;  kolla,  glue).    A  division  of  Protozoa. 

THE'CA  (Gr.  theke,  a  sheath).    A  sheath  or  receptacle. 

THE-CO-SOM'A-TA  /Gr.  ihelce  ;  and  soma,  body).  A  division  of  Pteropodous 
Molluscs,  in  which  the  body  is  protected  by  an  external  shell. 

THE-RI-O-MOR'PHA  (Gr.  therion,  beast ;  morphe,  shape).  Applied  by  Owen  to 
the  order  of  the  Tail-less  Amphibians  (Anoura). 

THO'RAX  (Gr.  for  a  breast-plate).    The  chest. 

THREAD-CELLS.     (See  Cnidse.) 

THYS-A-NU'RA  (Gr.  thusanoi,  fringes  ;  and  oura,  tail).  An  order  of  Apterous 
Insects. 

TIB'IA  (Lat.  for  a  flute).  The  shin-bone,  being  the  innermost  of  the  two  bones 
of  the  leg,  and  corresponding  with  the  radius  in  the  anterior  extremity. 

TO-TI-PAL'MA-TJB  (Lat.  totus,  whole  :  palma,  the  palm  of  the  hand).  A  group 
of  Wading  Birds  in  which  the  hallux  is  united  to  the  other  toes  by  mem- 
brane, so  that  the'feet  are  completely  webbed. 

TRA-CHE'A  (Gr.  tracheia,  the  wind-pipe).  The  tube  which  conveys  air  to  the 
lungs  in  the  air-breathing  Vertebrates. 

TRA-CHE'^E.    The  breathing-tubes  of  insects  and  other  articulate  animals. 

TRA-CHE-A'RI-A.  The  division  of  Arachnida  which  breathe  by  means  of  tra- 
cheae. 

TREM-A-TO'DA  (Gr.  trema,  a  pore ;  eidos,  form).    An  order  ofScolecida. 

TRICH'O-CYSTS  (Gr.  thrir,  hair ;  and  Tcustis,  a  cyst).  Peculiar  cells  found  in 
certain  Infusoria,  and  very  nearly  identical  with  the  "  thread-cells  "  of 
Ccelenterata. 

TRI-LOB'I-TA  (Gr.  treis,  three ;  lolos,  a  lobe).  An  extinct  order  of  Crustaceans. 

TRIT-O-ZO'OID  (Gr.  tritos,  third ;  zoijn,  animal ;  and  eidos,  form).  The  zooid 
produced  by  a  deuterozooid ;  that  is  to  say,  a  zooid  of  the  third  genera- 
tion. 


GLOSSARY.  351 

TRO'CHAL  (Gr.  trocJios,  a  wheel).  Wheel-shaped ;  applied  to  the  ciliated  disc 
of  the  Eotifera. 

TRO-CHAN'TER  (Gr.  trecho,  I  run).  A  process  of  the  upper  part  of  the  thigh- 
bone (femur)  to  which  are  attached  the  muscles  which  rotate  the  limb. 
There  may  be  two,  or  even  three,  trochanters  present. 

TRO'CHOID  (Gr.  trochos,  a  wheel ;  and  eidos,  form).  Conical,  with  a  flat  base ; 
applied  to  the  shells  of  Foraminiftra  and  Univalve  Molluscs. 

TRO'PHI  (Gr.  trophos,  a  nourisher).  The  parts  of  the  mouth  in  insects  which 
are  concerned  in  the  acquisition  and  preparation  of  food.  Often  called 
u  instrumenta  cibaria." 

TROPH'O-SOME  (Gr.  trepho,  I  nourish ;  and  soma,  bodv).  Applied  collectively 
to  the  assemblage  of  the  nutritive  zooids  of  any  Hydrozobn. 

TRTO'OA-TED  (Lat.  trunco,  I  shorten).  Abruptly  cut  off ;  applied  to  univalve 
shells,  the  apex  of  which  breaks  off,  so  that  the  shell  becomes  "  decol- 
lated." 

TU-BIC'O-LA  (Lat.  tuba,  a  tube ;  and  cola,  I  inhabit).  The  order  of  Annelida 
which  construct  a  tubular  case  in  which  they  protect  themselves. 

TU-BIC'O-LOUS.    Inhabiting  a  tube. 

TU-BU-LAR'I-DA. 

TU-NI-CA'TA  (Lat.  tunica,  a  cloak).  A  class  of  Molluscoida  which  are  envel- 
oped in  a  tough,  leathery  case  or  "  test." 

TUR-BEL-LA'RI-A  (Lat.  turbo,  I  disturb).     An  order  of  Scoledda. 

TUR'BI-NA-TED  (Lat.  turbo,  a  top).    Top-shaped ;  conical,  with  a  round  base. 

UL'NA  (Gr.  olene,  the  elbow).  The  outermost  of  the  two  bones  of  the  fore- 
arm, corresponding  with  \hzfibula  of  the  hind-limb. 

UM'BEL-LATE  (Lat.  umbella,  a  parasol).  Forming  an  umbel — i.  e.,  a  number 
of  nearly  equal  radii,  all  proceeding  from  one  point. 

UM-BIL'I-CUS  (Lat.  for  navel).  The  aperture  seen  at  the  base  of  the  axis  of 
certain  univalve  shells,  which  are  then  said  to  be  "perforated"  or  "  um- 
bilicated." 

UM'BO  (Lat.  for  the  boss  of  a  shield).    The  beak  of  a  bivalve  shell. 

UM-BREL'LA.     The  contractile  disc  of  one  of  the  Lucernarida. 

UN'CI-NATE  (Lat.  uncus,  a  hook).    Provided  with  hooks  or  bent  spines. 

UN-GUIC'U-LATE  (Lat.  unguis,  nail).    Furnished  with  claws. 

UN-GU-LA'TA  (Lat.  ungula,  hoof).  The  order  of  Mammals  comprising  the 
Hoofed  Quadrupeds. 

UN'GU-LATE.    Furnished  with  expanded  nails  constituting  hoofs. 

U-NI-LOC'U-LAR  (Lat.  unus,  one  ;  and  loculus,  a  little  purse).  Possessing  a 
single  cavity  or  chamber.  Applied  to  the  shells  of  Foraminifera  and  Mol- 
lusca. 

U'NI-VALVE  (Lat.  unus,  one  ;  valvce,  folding-doors).  A  shell  composed  of  a 
single  piece  or  valve. 

U-RO-DE'LA  (Gr.  oura,  tail ;  delos,  visible).  The  order  of  the  tailed  Amphi- 
bians (Newts,  etc.). 

UR'TI-OA-TING  CELLS  (Lat.  urtica,  a  nettle).    (See  Cnidse.) 

VAO'U-OLES  (Lat.  vacuus,  empty).  The  little  cavities  formed  in  the  interior 
of  many  of  the  Protozoa  by 'the  presence  of  little  particles  of  food,  usually 
surrounded  by  a  little  water.  These  are  properly  called  "  food-vacuoles,'' 
and  were  supposed  to  be  stomachs  by  Ehrenberg.  Also  the  clear  spaces 
which  are  often  seen  in  the  tissues  of  many  Ccelenterata. 

VAR'I-OES  (Lat.  -varix,  a  dilated  vein).  The  ridges  or  spinose  lines  which 
mark  the  former  position  of  the  mouth  in  certain  univalve  shells. 

VAS'OU-LAR  (Lat.  vas,  a  vessel).    Connected  with  the  circulatory  system. 

VE'LUM  (Lat.  for  a  sail).  The  membrane  which  surrounds  and  partially  closes 
the  mouth  of  the  "  disc"  of  Medusae,  or  medusiform  gonophores. 

VEN'TRAL  (Lat.  venter,  the  stomach).  Eelating  to  the  inferior  surface  of  the 
body. 

VEN'TRI-CXE  (Lat.  dim.  of  venter,  stomach).  Applied  to  one  of  the  cavities  of 
the  heart,  which  receives  blood  from  the  auricle. 


352  GLOSSARY. 

VEB'MES  (Lat.  vermis,  a  worm).  Sometimes  employed  at  the  present  day  in 
the  same,  or  very  nearly  the  same,  sense  as  Annuloida,  or  as  Annuloida 
plus  the  Anarthropoda. 

VER'MI-FORM  (Lat.  vermis,  worm  ;  snid/orma.  form).    Worm-like. 

VER'TE-BRA  (Lat.  verto,  I  turn).  One  of  the  bony  segments  of  the  vertebral 
column  or  back-bone. 

VER-TE-BRA'TA.  (Lat.  vertebra,  a  bone  of  the  back,  from  vertere,  to  turn). 
The  division  of  the  Animal  Kingdom  roughly  characterized  by  the  posses- 
sion of  a  back-bone. 

VES'I-CLE  (Lat.  vesica.  a  bladder).    A  little  sac  or  cyst. 

VI-BRAC'U-LA  (Lat.  Vidro,  I  shake).  Long  filamentous  appendages  found  in 
many  Polyzoa. 

VIB-RI-O'NES  (Lat.  vibro,  I  shake).  The  little  moving  filaments  developed  in 
organic  infusions. 

VIP-E-RI'NA  (Lat.  vipera,  a  viper).    A  group  of  the  Snakes. 

Vis'cE-RA. 

VI-VIP'A-ROTJS  (Lat.  vivus,  alive  ;  and  pario,  I  bring  forth).  Bringing  forth 
young  alive. 

WHORL.    The  spiral  turn  of  a  univalve  shell. 

XIPH-I-STER'HTJM  (Gr.  xiphos,  sword ;  sternon,  breast-bone).  The  inferior  or 
posterior  segment  of  the  sternum,  corresponding  with  the  "  xiphoid  carti- 
lage "  of  human  anatomy. 

XIPH-O-SU'RA  (Gr.  xiphos,  a  sword ;  and  oura,  tail).  An  order  of  Crustacea, 
comprising  the  Limuli  or  King-Crabs,  characterized  by  their  long  sword- 
like  tails. 

XY-LOPH'A-GOUS  (Gr.  xulon,  wood ;  and^Aa^o,  I  eat).  Eating  wood  ;  applied 
to  certain  Mollusca. 

ZO'OID  (Gr.  zoon,  animal ;  and  eidos,  form).  The  more  or  less  completely  in- 
dependent organisms,  produced  by  gemmation  or  fission,  whether  these  re- 
main attached  to  one  another  or  are  detached  and  set  free. 

ZO'O-PHYTE  (Gr.  zoon,  animal ;  phuton*  plant).  Loosely  applied  to  many 
plant-like  animals,  such  as  Sponges,  Corals,  Sea-anemones,  Sea-mats,  etc. 

ZO'O-SPOKES  (Gr.  zoon,  animal :  and  spora,  seed).  The  ciliated  locomotive 
germs  of  some  of  the  lowest  forms  of  plants  (Protophyta). 


QUESTIONS. 


1.  MENTION  some  of  the  characters  of  living  beings. 

2.  What  is  understood  by  "  organization  ?  " 
8.  Define  Biology  and  Zoology. 

4.  What  characters  separate  the  higher  animals  from  the  higher  plants  ? 

5.  How  does  the  nutrition  of  plants  differ  from  that  of  animals  ? 

6.  What  is  understood  by  "  classification  ?  " 

7.  What  is  the  basis  of  a  natural  and  scientific  classification  ? 

8.  Explain  the  terms  "morphology"  and  "physiology." 

9.  What  is  understood  by  "  sub-kingdoms,"  and  upon  what  characters 
are  these  founded  ? 

10.  What  are  the  great  Physiological  functions  ?     Define  these. 

11.  Explain  the  terms  "homology  "  and  "analogy,"  and  give  examples. 

12.  What  leading  characters  separate  the  Invertebrate  from  the  Verte- 
brate animals. 

13.  What  are  the  chief  characters  of  the  Protozoa? 

14.  What  is  sarcode  ? 

15.  What  are  cilia,  flagella,  and  pseudopodia? 

16.  Mention  the  three  great  classes  of  Protozoa. 

17.  What  is  the  structure  of  a  Gregarina,  and  where  would  you  expect  to 
find  one? 

1 8.  What  structures  characterize  the  Rhizopoda  ? 

19.  Describe  an  Amoeba. 

20.  What  is  the  so-called  "  contractile  vesicle  ?  " 

21.  What  is  meant  by  "fission? " 

22.  How  do  the  pseudopodia  of  the  Foraminifera  differ  from  those  of  an 
Amoeba  ? 

23.  What  structures  are  absent  in  the  Foraminifera,  which  occur  in  the 
Amoeba  ? 

24.  What  is  the  nature  of  the  shell  of  the  Foraminifera  ? 

25.  What  differences  subsist  between  a  perforated  and  an  imperforate 
shell  ?     Between  a  simple  and  a  compound  shell  ? 

26.  Where  do  Foraminifera  mostly  occur? 

27.  What  is  understood  by  "Distribution  in  Space"  and  "Distribution  in 
Time  ?  " 

28.  Mention  one  or  two  remarkable  fossil  Foraminifera. 

29.  What  is  Chalk  to  a  great  extent  composed  of? 

30.  What  is  the  nature  of  the  skeleton  of  the  Radiol"rin  / 

31.  Mention  some  example  of  the  Radiolaria. 


354  QUESTIONS. 

32.  Of  what  two  essential  elements  is  a  Sponge  composed  ? 

33.  What  is  the  nature  of  the  "  sponge-flesh  ?  " 

34.  Describe  the  circulation  of  water  in  a  Sponge.. 

35.  What  are  the  chief  variations  in  the  skeleton  of  Sponges  ? 

36.  Whence  are  the  Sponges  of  commerce  obtained  ? 

37.  How  do  the  Infusorian  Animalcules  derive  their  name  ? 

38.  By  what  leading  character  are  the  Infusoria  distinguished  from  tlie 
other  Protozoa  ? 

39.  Why  were  the  Infusoria  formerly  called  Polygastrica  ? 

40.  Describe  the  Bell-animalcule. 

41.  What  peculiarity  of  the  digestive  system  characterizes  the  sub-king- 
dom Ccdenterata  ? 

42.  Of  what  is  the  body  of  a  Coelenterate  animal  composed  ? 

43.  What  is  a  "  thread-cell  ?  " 

44.  Into  what  two  classes  are  the  CceJenterata  divided,  and  what  charac- 
ters distinguish  these  ?     Mention  examples  of  each. 

45.  What  is  understood  by  "  gemmation  ?  "     How  is  a  compound  animal 
or  colony  produced  ? 

46.  What  is  meant  by  the  term  "  zooid  ?  " 

47.  What  is  scientifically  understood  by  the  term  "  individual  ?  " 

48.  Define  the  terms  "  polypite,"  "  crenosarc,"  and  "  polypary." 

49.  Give  examples  of  the  Hydroid  Zoophytes. 

50.  Describe  shortly  the  structure  of  the  Hydra. 

51.  What  is  the  method  of  reproduction  in  the  Hydra  ? 

52.  What  peculiarities  distinguish  the  polypary  of  the  Corynida .« 

53.  Give  an  example  of  the  Corynida. 

54.  What  two  sets  of  zooids  go  to  form  the  colony  of  a  Hydroid  Zoo- 
phyte? 

55.  Define  the  terms  "  trophosome  "  and  "  gonosome." 

56.  What  is  a  "  gonophore  ?  " 

57.  What  is  a  "  medusiform  gonophore  ?  "     Why  is  it  so  called,  and  whai 
is  its  general  structure  ? 

58.  Give  an  example  of  the  Sertularida,  and  mention  the  differences 
which  distinguish  their  polypary  from  that  of  the  Cofynida. 

59.  What  is  a  "hydrothcca?" 

60.  Describe  the  general  structure  of  the  reproductive  bud  of  a  Cam- 
panularian. 

61.  How  do  the  Oceanic  Hydrozoa  differ  from  the  Hydroid  Zoophytes  ? 

62.  What  is  a  "  nectocalyx,"  and  what  is  its  structure  ? 

63.  What  is  a  "bract?" 

64.  Mention  examples  of  the  Oceanic  Hydrozoa. 

65.  What  is  the  "  float "  or  "  pneumatophore  "  of  the  Physophoridce  ? 

66.  Of  what  real  nature  are  many  of  the  so-called  Medusae  or  Jelly-fishes  ? 

67.  What  is  the  general  structure  of  a  Medusa,  and  with  what  structure 
in  the  Hydroid  Zoophytes  does  it  agree  ? 

68.  From  what  circumstance  is  the  name  "  naked-eyed  "  Medusae  derived  ? 

69.  What  are  the  "marginal  bodies  "  of  the  Medusce? 

70.  Describe  Lucernaria. 

71.  Of  what  nature  are  the  great  Sea-blubbers  ? 

72.  Describe  "Hydra-tuba"  and  its  development. 

73.  What  is  the  structure  of  a  "  Hidden-eyed  Medusa "  or  Sea-blubber, 
and  from  what  circumstance  is  the  former  name  derived  ? 

74.  Differences  between  the  naked-eyed  and  hidden-eyed  Medusas  ? 

75.  Describe  the  generative  bud  of  Khizostoma. 


QUESTIONS.  355 

76.  Give  the  leading  characters  of  the  Actinozoa. 

77.  How  does  the  transverse  section  of  a  Hydrozoon  differ  from  that  of 
an  Actinozoon  ? 

78.  What  is  a  "polype?" 

79.  Describe  a  Sea-anemone. 

80.  What  are  the  "mesenteries  "  of  a  Sea-anemone,  and  what  organs  do 
they  carry  ? 

81.  What  is  a  "  coral  ?  " 

82.  What  are  the  "  septa  "  of  a  coral,  and  to  what  part  of  the  living 
animal  do  they  correspond  ? 

83.  What  are  coral-reefs,  where  do  they  occur  most  abundantly,  and  what 
are  the  chief  varieties  which  occur  ? 

84.  How  do  the  Alcyonaria  differ  numerically  from  the  Zoantharia  ? 

85.  Mention  some  example  of  the  Alcyonaria. 

86.  In  what  Alcyonarian  is  there  a  well-developed  sclerodermic  coral  ? 

87.  Of  what  nature  is  the  sclerobasic  coral  of  the  Gorgonidce? 

88.  Mention  a  well-known  example  of  the  Gorgonidce. 

89.  Give  the  leading  characters  of  the  Ctenophora. 

90.  What  is  a  "  ctenophore  ?  " 

91.  Is  a  nervous  system  present  in  any  of  the  Actinozoa,  except  in  the 
Ctenophora  ? 

92.  Mention  an  example  of  the  Ctenophora. 

93.  What  animals  belong  to  the  Echmodermata,  and  whence  is  the  name 
of  the  class  derived  ? 

94.  What  is  understood  by  "  bi-lateral  symmetry  ?  " 

95.  At  what  time  of  life  are  the  Ecliinoderms  bi-laterally  symmetrical, 
and  what  is  their  condition  in  this  respect  when  adult  ? 

96.  What  is  a  water-vascular  system,  what  is  it  called  in  this  class,  and 
what  special  function  does  it  generally  discharge  ? 

97.  What  is  the  arrangement  of  the  nervous  system  in  Echinoderms  ? 

98.  What  distinguishes  the  Sea-urchins  from  other  Echinoderms  ? 

99.  Into  how  many  zones  may  the  test  of  a  living  Sea-urchin  be  divided, 
and  how  many  rows  of  plates  are  contained  in  each  zone? 

100.  What  are  the  "  ambulacral "  and  "  inter-ambulacral  areas  ?  " 

101.  What  plates  are  always  placed  at  the  summit  of  the  shell  ? 

102.  What  is  the  "  madreporiform  tubercle  ?  " 

103.  Describe  the  general  nature  of  the  spines  and  their  function. 

104.  What  are  "  pedicellariae  ?  " 

105.  What  are  the  "  tube-feet  ?  "     Describe  the  general  arrangement  of 
the  u  ambulacral  system." 

106.  What  is  the  structure  of  the  circulatory  and  nervous  organs  in  the 
Echinus  ? 

107.  Mention  a  peculiarity  in  the  development  of  the  Echinus. 

108.  Give  the  leading  characters  of  the  Star-fishes. 

109.  What  peculiarities  distinguish  the  arms  of  Star-fishes  ? 

110.  What  is  the  structure  of  the  stomach  in  Star-fishes  ? 

111.  How  do  the  Brittle-stars  resemble  the  true  Star-fishes,  and  how  are 
they  distinguished  ? 

112.  What  is  the  structure  of  the  digestive  system  in  Brittle-stars? 

113.  What  is  the  essential  peculiarity  of  the  "Crinoids? 

114.  Mention  a  living  Crinoid  which  is  free  when  adult,  and  one  which  is 
permanently  fixed. 

115.  What  is  the  general  shape  of  the  Holothurians,  and  the  nature  of 
their  integuments  ? 


356  QUESTIONS. 

116.  What  is  the  condition  of  the  ambulacral  system,  and  where  is  the 
*  madreporiform  tubercle  "  situated  ? 

117.  What  is  the  mouth  surrounded  by? 

118.  What  is  the  "  respiratory  tree  "  of  the  Holothurians  ? 

119.  What  characters  distinguish  the  Scolecida  ?   How  are  they  separated 
from  the  Echinoderms  ? 

120.  What  is  meant  by  the  term  Entozoa? 

121.  In  what  relation  do  the  Bladder-worms  stand  to  the  Tape-worms  ? 

122.  What  is  the  structure  of  an  ordinary  Tape-worm? 

123.  Give  the  structure  of  the  "head"  and  of  a  single  joint,  and  state 
what  is  the  relation  of  the  head  to  the  joints. 

124.  State  shortly  the  process  of  development  in  a  Tape-worm. 

125.  What  is  the  "  measles  "  of  the  Pig  ? 

126.  What  are  "  hydatids  "  in  man  ? 

127.  What  are  the  characters  of  the  Trcmatode  worms?     Mention  an  ex- 
ample. 

128.  What  is  the  "  rot "  of  Sheep  caused  by  ? 

129.  What  groups  of  animals  are  included  in  the  lurbellaria? 

130.  Give  an  example  of  the  Acanthocephala,  and  state  the  character  from 
which  the  name  is  derived. 

131.  Where  do  the  Gordiacea  spend  the  earlier  part  of  their  existence, 
and  what  is  their  common  name  ? 

132.  Mention  examples  of  the  Nematode  worms. 

133.  From  what  do  the  Wheel-animalcules  get  their  name  ? 

134.  What  is  the  general  size  of  the  Rotifers,  and  where  are  they  found  ? 

135.  What  marked  differences  are  there  between  the  males  and  females  ? 

136.  What  are  the  functions  of  the  ciliated  "wheel? " 

137.  Give  the  general  anatomy  of  a  Rotifer. 

138.  Give  the  leading  characters  of  an  Annulose  animal. 

139.  Into  what  great  divisions  is  the  sub-kingdom  Annulosa  divided,  and 
what  are  the  characters  of  these  ? 

140.  What  is  the   general  structure   of  one   of  the  rings  of  an  An- 
nelifle  ? 

141.  What  is  the  "  pseudohaemal  system  "  of  the  Annelida,  and  to  what 
is  it  believed  to  correspond  ? 

142.  What  are  the  characters  of  the  Hirudmea* 

143.  To  what  does  the  Medicinal  Leech  owe  its  value  ? 

144.  How  is  locomotion  effected  in  the  Leeches  ? 

145.  How  are  the  Oligochceta  distinguished? 

146.  What  are  the  locomotive  organs  of  the  Earth-worm  ? 

147.  Of  what  nature  are  the  breathing-organs  of  the  Tubicola,  and  where 
are  they  placed  ? 

148.  Mention  a  common  Tubicolous  Annelide. 

149.  To  what  do  the  Errantia  owe  their  name,  and  what  are  their  loco- 
motive organs  ? 

150.  Where  are  the  gills  placed  in  the  Errantia? 

151.  What  orders  of  Annelida  possess  gills,  and  which  have  not  ? 

152.  Give  the  general  characters  of  Articulate  animals. 

153.  Give  the  characters  of  the  Crustacea. 

154.  How  many  segments  go  to  the  body  of  a  Crustacean,  and  into  what 
distinct  regions  may  these  be  distributed  ? 

155.  What  is  understood  by  the  "  cephalothorax  ?  " 

156.  To  what  section  of  Crustacea  does  the  Lobster  belong  ? 

157.  What  is  the  "carapace"  of  the  Lobster  ? 


QUESTIONS.  357 

158.  What  is  the  part  generally  called  the  "  tail,"  and  what  is  the  so- 
called  "  head  ?  " 

159.  What  are  the  "  antennae,"  and  how  many  are  there  hi  the  Lobster 
and  in  Crustacea  generally  ? 

160.  What  are  "foot-jaws,"  and  why  are  they  so  called? 

161.  What  are  "  chelaa  ?  " 

162.  Of  what  nature  are  the  appendages  of  the  abdomen  in  the  Lobster  ? 

163.  What  is  the  last  segment  of  the  abdomen  called  ? 

164.  Describe  the  gills  of  the  Lobster.     Where  are  they  placed  ? 

165.  Of  what  nature  is  the  abdomen  of  the  Hermit-crabs  ? 

166.  How  are  the  Crabs  distinguished  from  the  Lobsters? 

167.  By  what  character  does  the  young  Crab  approach  the  Lobster? 

168.  Give  an  example  of  the  Isopoda  ? 

169.  What  is  the  character  of  the  appendages  of  the  mouth  in  the  King- 
Crabs  ? 

170.  What  is  the  structure  of  a  Trilobite  ? 

171.  What  is  the  nature  of  the  shell  of  the  Ostracode  Crustaceans  ? 

172.  What  change  do  the  Cirripedes  undergo  in  passing  from  the  larval 
to  the  adult  condition  ? 

173.  What  are  the  two  types  of  the  Cirripedes  ?     Give  examples. 

174.  Give  the  general  characters  of  the  Arachnida? 

175.  What  is  the  structure  of  the  mandibles  of  the  Spiders  ?     Of  the 
Scorpions  ? 

176.  To  what  do  the  mandibles  of  the  Arachnida  correspond? 

177.  Of  what  nature  are  the  breathing-organs  of  the  Arachnida? 

178.  What  is  the  structure  of  tracheae?     Of  pulmonary  sacs  ? 

179.  What  are  the  organs  of  vision  in  the  Arachnida  ? 

180.  What  are  the  habits  of  the  Mites  ?     Give  examples. 

181.  By  what  structure  do  the  Scorpions  inflict  wounds  ? 

182.  What  is  the  condition  of  the  abdomen  in  Scorpions  ?     In  Spiders  ? 

183.  By  means  of  what  organs  do  the  Spiders  spin  webs? 

184.  What  are  the  general  characters  of  the  Myriapoda? 

185.  What  is  the  general  condition  of  the  young  Myriapod? 

186.  What  are  the  distinctions  between  the  Centipedes  and  Millipedes? 

187.  What  is  the  number  of  legs  in  Pauropus? 

188.  What  are  the  general  characters  of  Insects? 

189.  What  organs  are  carried  by  the  head  in  Insects  ? 

190.  How  many  segments  form  the  thorax,  and  what  appendages  do  they 
always  carry  ?     What  appendages  do  they  sometimes  carry  ? 

191.  What  are  "  nervures  ?  " 

192.  How  many  rings  generally  go  to  the  abdomen  of  Insects  ?     What 
appendages  (if  any)  do  these  support  ? 

193.  What  are  the  chief  modifications  in  the  organs  of  the  mouth  in 
Insects  ? 

194.  Describe  the  digestive  system  of  an  Insect? 

195.  How  is  the  circulation  carried  on  ? 

196.  Of  what  nature  are  the  breathing-organs  ? 

197.  Of  what  nature  are  the  eyes  in  Insects  ? 

198.  What  is  understood  by  the  "metamorphosis  "  of  an  Insect  ? 

199.  What  are  the  chief  differences  in  the  metamorphoses  of  Insects  ? 

200.  What  peculiarity  distinguishes  the  adult  state   of  Insects   which 
undergo  no  metamorphosis  ? 

201.  What  is  understood  by  the  terms  "larva,"  "pupa,"  and  "imago  ?  " 

202.  What  is  a  "  chrysalis  ?  "     A  "  cocoon  ?  " 


358  QUESTIONS. 

203.  What  are  the  more  important  Insects  which  pass  through  no  meta- 
morphosis ? 

204.  'The  chief  characters  of  the  Hemiptera  ?     Give  examples. 

205.  What  are  "  hemelytra  ?  " 

208.  The  chief  characters  of  the  Orthoptcra  ?     Give  examples. 

207.  The  chief  characters  of  the  Neuroptera?     Give  examples. 

208.  What  members  compose  a  colony  of  White  Ants  or  Termites  ? 

209.  The  chief  characters  of  the  Aphaniptera  ?     Give  an  example. 

210.  The  chief  characters  of  the  IHptera?     Give  examples. 

211.  The  chief  characters  of  the  Lepidoptera? 

212.  Characters  of  the  larvae  of  Lepidoptera  ? 

213.  What  characters  distinguish  Butterflies  and  Moths  respectively? 

214.  Chief  characters  of  Hymenoptera  ?     Give  examples. 

215.  Give  some  account  of  the  social  communities  of  Bees  and  Ants  ? 

216.  What  is  the  condition  of  the  wings  in  Strepsiptcra  ? 

217.  Chief  characters  of  Coleoptera  ?     Give  examples. 

218.  What  are  "  elytra  ?  " 

219.  Mention  a  useful  Beetle. 

220.  Chief  characters  of  the  Mollusca? 

221.  Condition  of  nervous  system  in  Mollusks  ?     Of  circulatory  system  ? 
Of  breathing-organs  ?     Of  digestive  system  ? 

222.  Primary  divisions  of  Mollusca,  and  the  characters  of  these  ? 

223.  Chief  characters  of  the  Polyzoa  ? 

224.  Explain  the  term  "  polypide  ?  " 

225.  How  is  the  polypide  of  a  Polyzobn  distinguished  from  the  polypite 
of  a  Hydrozoon  ? 

226.  Structure  of  a  single  "  polypide.  " 

227.  What  are  "  bird's-head  processes,"  and  to  what  may  they  be  com- 
pared ? 

228.  What  general  distinction  is  there  between  the  fresh-water  and  marine 
Polyzoa  ? 

229.  Chief  characters  of  Tunicata  ? 

230.  Nature  of  the  "  test  ?  " 

231.  Structure  of  the  heart  in  Tunicata? 

232.  Distinctions  between  simple,  social,  and  compound  Tunicates  ? 

233.  Chief  characters  of  Brachiopoda  ? 

234.  Nature  of  the  shell,  as  compared  with  that  of  Bivalves  ? 

235.  Structure  and  nature  of  the  "  arms  ?  " 

236.  Chief  characters  of  the  Lamdlibranchiata  ?     Give  examples. 

237.  Nature  and  uses  of  the  "  foot  ?  " 

238.  Nature,  uses,  and  number  of  the  "  adductor  muscles  ?  " 

239.  What  are  the  "  muscular  impressions  "  and  the  "  pallial  line  ?  " 

240.  Structure   and    mode   of  opening,   and    connection    between,  the 
valves  ? 

241.  Structure  of  the  respiratory  organs  ? 

242.  Nature  and  uses  of  the  "  respiratory  siphons  ?  " 

243.  Condition  of  circulatory  system  ?     Of  digestive  system  ? 

244.  Condition  of  young  when  first  hatched  ? 

245.  Chief  characters  of  the  Gasteropoda  ?    Give  examples.    Why  spoken 
of  as  "  univalves  .*" 

246.  What  is  the  "  operculum  ?  " 

247.  Compare  the  Gasteropoda  with  the  Lamellibranchiata  as  regards  the 
head. 

248.  What  is  the  nature  of  the  "  odontophore  ?  " 


QUESTIONS.  359 

249.  Condition  of  the  heart  and  breathing-organs  ? 

250.  What  divisions  of  the  Gasteropoda  may  be  founded  on  the  nature  of 
the  breathing-organs  ? 

251.  Condition  of  the  young  water-breathing  Gasteropod  ? 

252.  Structure  and  modifications  of  the  shell  in  Gasteropods  ? 

253.  What  are  the  two  leading  conditions  of  the  mouth  of  the  shell  ? 

254.  General  characters  of  the  Nudibranchiata  ? 

255.  Nature  of  the  foot  in  the  Heteropoda  ? 

256.  General  characters  of  the  air-breathing  Gasteropods  ? 

257.  General  characters  of  the  Ptcropoda? 

258.  General  characters  of  the  Cephalopoda? 

259.  Nature  of  the  "arms"  and  their  suckers  in  the  Cuttle-fishes? 

260.  Structure  of  the  "  funnel  ?  " 

261.  Nature  of  the  ink-bag  ?     What  living  Cephalopod  is  without  an  ink- 
bag? 

262.  Nature  of  the  breathing-organs  ?     Of  the  circulatory  organs  ?     Of 
the  respiratory  process  ?     Of  the  nervous  system  ? 

263.  Peculiarities  in  the  reproductive  process  in  the  Cuttle-fishes  ? 

264.  Nature  of  the  internal  shell  of  the  Cuttle-fishes  ? 

265.  What  two  living  Cephalopods  possess  an  external  shell,  and  ^vilat 
are  the  differences  between  these  ? 

266.  Characters  of  the  Dibranchiate  Cephalopods  ?     Give  examples. 

267.  Describe  the  shell  of  the  Argonaut  ? 

268.  Characters  of  the  Tetrabranchiate  Cephalopods  ? 

269.  Describe  the  shell  of  the  Pearly  Nautilus  ? 

270.  Mention  some  fossil  forms  allied  to  the  Pearly  Nautilus  ? 

271.  General  characters  of  the  Vertebrata? 

272.  What  is  the  "  notochord  ?  " 

273.  General  structure  of  a  "  vertebra  ?  " 

274.  Kegions  generally  recognizable  in  the  vertebral  column  ? 

275.  General  structure  of  the  fore-limb  ? 

276.  General  structure  of  the  hind-limb  ? 

277.  General  structure  of  the  digestive  system  ? 

278.  Source  of  the  blood  ?     Nature  of  the  "  blood-corpuscles  ?  " 

279.  What  Vertebrate  animal  has  no  heart  ? 

280.  General  nature  of  the  respiratory  organs  ? 

281.  What  is  the  difference  between  a  gill  and  a  lung  ? 

282.  General  structure  of  the  nervous  system  ? 

283.  Define  the  terms  "oviparous,"  "viviparous,"  and  " ovo- viviparous." 

284.  Into  what  primary  sections  are  the  Vertebrata  divided  by  Huxley  ? 

285.  What  are  the  five  classes  of  Vertebrates  ? 

286.  General  characters  of  Fishes  ? 

287.  Chief  forms  of  scales  ? 

288.  Nature  of  the  "  lateral  line  ?  " 

289.  Form  of  the  vertebrae  of  a  Fish  ? 

290.  Position  and  connections  of  the  ribs  ? 

291.  Nature  of  the  "  interspinous  bones  ?  " 

292.  Nature  and  position  of  the  limbs  of  Fishes  ? 

293.  Distinction  between  the  "  paired  "  and  "  median  fins  ?  " 

294.  Number  and  names  of  the  median  fins  ? 

295.  Difference  between  homocercal  and  heterocercal  tail  ? 

296.  What  are  the   "rays?"      Difference  between  "soft  rays"  an<J 
"  spinous  rays  ?  " 

297.  What  are  the  "  pyloric  cseca  ?  " 


360  QUESTIONS. 

298.  General  arrangement  of  the  gills  in  a  Bony  Fish  ? 

299.  Structure  of  the  heart  and  course  of  the  circulation  in  a  typical  Fish  ? 

300.  What  is  the  "  swim-bladder,"  and  to  what  does  it  correspond  ? 

301.  Nature  of  the  swim-bladder  hi  the  Mud-fish  ? 

302.  Condition  of  the  organ  of  hearing  ?  of  the  nose  ? 

303.  In  what  Fishes  does  the  nose  open  behind  into  the  throat  ? 

304.  General  characters  of  the  Lancelet  ? 

305.  General  characters  of  the  Marsipobranchii  ?     Give  examples. 

306.  Nature  of  the  respiratory  organs  in  the  Lampreys  ? 

307.  General  characters  of  Teleostei?     Give  examples. 

308.  General  characters  of  the  Oanoidei  ?     Give  examples. 

309.  Condition  of  the  vertebrae  in  the  Bony  Pike  ? 

310.  General  characters  of  the  Elasmobranchii  ?     Give  examples. 

311.  General  characters  of  the  Dipnoi? 

312.  Distribution  of  the  Mud-fishes? 

313.  General  characters  of  the  class  Amphibia? 

314.  Nature  of  the  metamorphosis  in  Amphibians  ? 

315.  General  characters  of  the  Ophiomorpha?     Give  examples. 

316.  General  characters  of  Urodela?     Give  examples. 

317.  Explain  the  terms  "  perennibranchiate  "  and  "  caducibranchiate." 

318.  Distinctions  between  Tailed  Amphibians  and  Lizards? 

319.  General  characters  of  the  Anoura?     Give  examples. 

320.  Phenomena  of  the  development  of  a  Frog  ?     What  general  zoologi- 
cal law  is  illustrated  thereby  ? 

321.  General  characters  of  the  Sauropsida  ? 

322.  General  characters  of  Reptiles  ? 

323.  Structure  of  the  lower  jaw,  and  its  connections  with  the  skull  ? 

324.  General  nature  of  the  teeth  ? 

325.  In  what  Reptiles  are  the  teeth  sunk  in  sockets  ? 

326.  How  does  the  intestine  terminate  in  Reptiles  ? 

327.  Structure  of  the  heart  and  course  of  the  circulation  in  Reptiles 
generally  ? 

328.  Condition  of  the  heart  in  the  Crocodiles  ? 

329.  General  characters  of  the  Chelonia  ?     Give  examples  ? 

330.  Leading  peculiarities  in  the  skeleton  of  Chdonia  ? 

331.  Chief  groups  of  Chelonians  ?     Give  examples. 

332.  General  characters  of  the  Ophidia? 

333.  Condition  of  the  limbs  in  Snakes  ? 

334.  Mode  of  progression  in  Snakes  ?  . 

335.  Structure  of  the  tongue  ?  of  the  eye  ? 

336.  Structure  and  connections  of  the  lower  jaw  ? 

337.  General  structure  and  function  of  the  teeth  ? 

338.  Nature  of  the  teeth  in  the  non-venomous  and  poisonous  Snakes 
respectively  ? 

339.  Examples  of  harmless  Snakes  ? 

340.  Examples  of  poisonous  Snakes  ? 

341.  General  characters  of  the  Lacertilia?     Give  examples. 

342.  Characters  which  separate  the  snake-like  Lizards  from  the  true 
Serpents  ? 

343.  Peculiarities  of  the  Flying  Dragon  ? 

344.  General  characters  of  the  Crocodilia  ? 

345.  Differences  between  Crocodiles  and  Alligators,  and  the  geographical 
distribution  of  each  ? 

346.  Peculiarity  of  the  Gavial,  and  its  geographical  distribution  ? 


QUESTIONS.  361 

347.  Leading  characters  of  the  Ichthyopterygia  ? 

348.  Characters  separating  Plesiosaurus  from  Ichthyosaurus  ? 

349.  Leading  characters  of  Pierosauria  ? 

350.  General  characters  of  Birds  ? 

351.  General  structure  of  a  quill-feather  ? 

352.  Peculiarity  of  the  feathers  of  the  Ostrich  ? 

353.  Characters  of  the  backbone  in  Birds  ? 

354.  Nature  and  position  of  the  "  ploughshare  "  bone  ? 

355.  Structure  of  the  beak  ? 

356.  Nature  of  the  "  sternal  ribs  ?  " 

357.  Form  of  the  sternum  in  Birds  which  fly  ?     In  those  which  do  not 
fly? 

358.  Structure  of  the  shoulder-girdle  ? 

359.  Nature  and  function  of  the  "  merry-thought  ?  " 

360.  General  structure  of  the  fore-limb  or  wing  ? 

361.  General  structure  of  the  hind-limb  ? 

362.  Nature  of  the  "  tarso-metatarsus  ?  " 

363.  Number  and  position  of  the  toes  ? 

364.  What  bird  possesses  only  two  toes  ? 

365.  What  is  the  "  cere  ?  " 

366.  General  structure  of  the  digestive  system  in  Birds  ? 

367.  Condition  of  gizzard  in  flesh-eating  and  grain-eating  Birds  respec- 
tively ? 

368.  What  are  the  "  intestinal  caeca  ?  " 

369.  Structure  and  peculiarities  of  the  lungs  ? 

370.  Structure  and  functions  of  the  air-sacs  ? 

371.  What  is  meant  by  a  bone  being  "pneumatic  ?  " 

372.  In  what  cases  are  the  bones  not  pneumatic  ? 

373.  General  structure  of  the  heart  and  course  of  the  circulation  in  Birds  ? 

374.  What  is  "  incubation,"  and  why  are  Birds  specially  adapted  for  this 
process  ? 

375.  What  differences  subsist  in  the  condition  of  the  young  bird  at  birth  ? 

376.  What  peculiarities  distinguish  the  eye  of  Birds  ? 

377.  What  is  the  "  membrana  nictitans  ?  " 

378.  What  peculiarities  distinguish  the  ear  of  Birds  ? 

379.  What  Birds  have  a  rudimentary  external  ear  ? 

380.  General  characters  of  the  Natatores?     Give  examples. 

381.  General  characters  of  the  Grallatores?     Give  examples. 

382.  General  characters  of  the  Cursores? 

383.  Mention  some  of  the  more  remarkable  Cursorial  Birds,  and  state 
something  as  to  their  peculiarities  and  geographical  distribution. 

384.  General  characters  of  the  Rasores  ? 

385.  Characters  and  examples  of  the  Gallinaceous  Birds  ? 

386.  Characters  and  examples  of  the  Columbaceous  Birds  ? 

387.  Mention  an  extinct  Columbaceous  Bird. 

388.  General  characters  of  the  Scansores? 

389.  Leading  families  of  the  Scansores? 

390.  General  characters  of  the  Insessores? 

391.  Mention  the  four  sections  into  which  the  Insessores  are  divided,  and 
state  the  peculiarities  distinguishing  these. 

392.  Give  examples  of  each  of  these  sections. 

393.  General  characters  of  the  Raptores? 

394.  Distinctions  between  Nocturnal  and  Diurnal  Birds  of  Prey  ? 

395.  Characters  of  the  Saururce  ? 


362  QUESTIONS. 

396.  For  what  bird  has  this  order  been  established  ? 

397.  General  characters  of  the  Mammalia? 

398.  General  structure  of  the  backbone  ? 

399.  General  number  of  cervical  vertebras? 

400.  Distinction  between  "  true  "  and  "  false  "  ribs  ? 

401.  General  structure  of  limbs  ? 

402.  What  Mammals  have  no  teeth  ? 

403.  What  are  the  "  milk-teeth  ?  " 

404.  Describe  the  general  groups  of  teeth  in  a  Mammal. 

405.  What  is  the  "  diaphragm  ?  " 

406.  General  structure  of  the  heart  and  course  of  the  circulation  ? 

407.  General  structure  of  the  lungs  ? 

408.  What  is  the  "  corpus  callosum  ?  " 

409.  What  Mammals  possess  no  external  ear  ? 

410.  Mention  some  modifications  of  the  integumentary  appendages  in 
Mammals. 

411.  What  Mammals  are  without  hair  when  adult? 

412.  What  are  the  mammary  glands? 

413.  What  is  the  "  placenta  ?  " 

414.  General  characters  of  the  Monotremata? 

415.  Mention  the  animals  included  in  the  Monotremata,  and  state  their 
geographical  distribution. 

416.  What  are  the  "  marsupial  bones  ?  " 

417.  General  characters  of  the  Marsupialia? 

418.  Geographical  distribution  of  the  Marsupials? 

419.  Give  examples  of  the  Marsupials. 

420.  General  characters  of  the  Edentata  ? 

421.  Geographical  distribution  of  the  order? 

422.  Leading  groups  of  the  Edentata,  and  their  distinguishing  charac- 
ters? 

423.  General  characters  of  the  Sirenia? 

424.  Existing  forms  of  the  Sirenia  ? 

425.  General  characters  of  the  Cetacea? 

426.  Give  examples  of  the  Whalebone  Whales  and  Toothed  Whales. 

427.  What  is  the  "blowing"  of  a  Whale  ? 

428.  What  characters  distinguish  the  Dolphins  ? 

429.  Nature  of  the  tusk  of  the  Narwhal  ? 

430.  General  characters  of  the  Ungulata  ? 

431.  Divisions  of  Unyulata  and  their  characters  ? 

432.  Nature  and  position  of  the  horns  of  Rhinoceros? 

433.  Characters  and  distribution  of  the  Tapirs  ? 

434.  Characters,   chief   forms,   and    geographical    distribution  of   the 


435.  Characters  and  distribution  of  the  Hippopotamus  ? 

436.  Characters  of  the  Suida  ?     Leading  forms  ? 

437.  General  characters  of  the  Ruminants  ? 

438.  Structure  of  the  stomach  in  Ruminants  ? 

439.  Characters  and  distribution  of  Camelidce? 

440.  Characters  and  distribution  of  Cervidce  ? 

441.  Nature  of  the  horns  of  Cervidce? 

442.  Characters  and  distribution  of  the  Giraffe  ? 

443.  Characters  and  leading  forms  of  the  Cavicornia  ? 

444.  General  characters  and  distribution  of  the  Hyracoidea  ? 

445.  General  characters  and  distribution  of  Proboscidea  ? 


QUESTIONS.  363 

446.  Distinctions  between  the  Indian  and  African  Elephants  ? 

447.  General  characters  of  the  Camivora? 

448.  Sections  into  which  the  Camivora  are  divided,  and  the  characters 
of  these  ? 

449.  Characters  of  the  Seals  ? 

450.  Dentition  of  the  Walrus  ? 

451.  Characters  of  the  Bears  ? 

452.  Other  Plantigrade  Camivora  ? 

453.  Characters  and  examples  of  the  Mustdidce? 

454.  Examples  of  the  Melidce? 

455.  Examples  of  the  Viverridce? 

456.  Characters  and  examples  of  the  Canidce? 

457.  Characters  and  distribution  of  Hycenidce  ? 

458.  Characters  and  distribution  of  the  Felidce? 

459.  General  characters  of  the  Rodentia? 

460.  Structure  of  the  incisor  teeth  of  Rodents  ? 

461.  Leading  families  of  the  Rodentia? 

462.  General  characters  of  the  Cheiroptera  * 

463.  What  is  the  "  patagium  "  of  Bats  ? 

464.  Sections  of  the  Cheiroptera,  and  their  distribution* 

465.  General  characters  of  the  Insectivora  ? 

466.  Characters  and  examples  of  the  Talpidce? 

467.  Characters  and  examples  of  the  Soricidce? 

468.  Characters  and  examples  of  the  Erinaceidce  / 

469.  Other  Insectivora  ? 

470.  Characters  and  distribution  of  the  Flying-Lemurs  ? 

471.  General  characters  of  the  Quadrumana? 

472.  Characters  and  distribution  of  the  Strepsirhina  ? 

473.  Examples  of  Strepsirhina  ? 

474.  Characters  and  distribution  of  Platyrhina  ? 

475.  Examples  of  Platyrhine  Monkeys  ? 

476.  Characters  and  distribution  of  Catarhina  ? 

477.  General  characters  of  the  Baboons  ? 

478.  Characters  and  examples  of  the  Anthropoid  Apes  ? 

479.  General  characters  of  the  order  Bimana? 


INDEX. 


Acanthocephala,  109  ;  general  characters  of, 

Acanthometra,  38,  39. 
Acanthophis,  245. 
Acanthopteri,  219. 
Acarina,  141. 
Achetina,  155. 
Acorn-shells,  136,  13,. 
Acrydium,  156. 
Actinia,  51,  SB. 


,  52,  53  ;  general  Characters  of,  84  ; 
orders  of,  86-94. 
Adjutant,  269. 
Agouti,  311. 
AUurus,  308. 

Air-receptacles  of  Birds.  261. 
Alcedinidce,  277. 
Alces,  301. 
Alcidae,  267. 

Alcyonaria,  86;  characters  of,  90. 
Alcyonium,  90. 

ul^CB,  4. 

Alligator,  248. 

Alpaca,  301. 

Amblystoma,  228. 

Ainbulacral  system  of  Echinus.  18,  99. 

Ameiva,  245. 

Ametabolic  Insects,  150,  153. 

Ammonites,  195. 

Amo&ba,  30  ;  nucleus  of,  32  ;  reproduction  of, 

Amo&bea,  30. 

Amphibia,  195,  205;  general  characters  of, 

225;  orders  of,  226-233. 
Amphioxus,  214,  215. 
Amphipoda,  138. 
Anacanthini,  219. 
Analogy,  15. 
Anarthropoda,  119. 
Anatidce,  267. 
Anguillula,  115. 
^wgrww,  245,  246. 

Animals  and  plants,  differences  between,  3-6. 
Annelida,  119;  general  characters  of,  120; 

typical   segment   of,    120;     divisions   of; 

Annuloida,  15  ;  characters  and  divisions  of, 

95. 

Annulosa,  15;  general  characters  of,  118. 
Anomodontia,  237,  252. 
Anomura,  131. 


Anoplura,  153. 

Anoura,  226,  230,  232. 

Anserince,  267. 

Ant-eaters,  282,  286. 

Antelopes,  803. 

Antenna;,  124, 139, 149. 

Anthropoid  Apes,  317. 

Ant-lion,  156. 

Ants,  161,  162. 

Apes,  315,  81T. 

Aphaniptera,  158. 

Aphides,  154, 155. 

Aphis-lion,  156, 157. 

Aphrodite,  124, 125. 

Apidce,  160. 

Aplacental  Mammals,  286,  287. 

Aptera,  150. 

Apteryx,  270,  271. 

Apus,  138. 

Aquiferous  system  (Sponges),  41. 

Arachnaetis,  86. 

Arachnida,  127;  general  characters  of  139; 
orders  of,  140-144. 

Araneida,  142. 

Archceopteryx,  279. 

Arctomys,  312. 

Ardea,  269. 

Ardeidw,  269. 

Arenicola,  124, 125. 

Argonauta,  190, 191. 

Armadillos,  286. 

Arms,  of  Srachiopoda,  175;  of  Cephalo- 
poda, 188,  190,  191. 

Arthropoda,  119;  general  characters  of,  126. 

Articulata,  126. 

Artiodactyla,  297,  298. 

Ascaris,  115. 

Ascidian  Mollusks,  171 ;  solitary,  social,  and 
compound,  173. 

Asinus,  298. 

Ass,  298. 

Asteroidea,  96;  general  characters  of,  100, 
101. 

Atolls,  89.  90. 

Atrium  (Tunicata),  173. 

Auchema.  301. 

Aurelia,  80. 

Aves,  205 ;  general  characters  of,  253 ;  feath- 
ers of,  253;  vertebral  column  of,  254;  beak 
of,  255;  pectoral  arch  of,  255;  hind-limb  of, 
257;  foot  of,  258;  digestive  system  of,  258; 
respiratory  system  of,  260;  circulatory 


IXDEX. 


365 


system  of,  261 ;  nervous  system  and  organs 
of  sense  of,  262,  263 ;  orders  oi;  265. 

Axolotl,  227,  228. 

Aye- Aye,  316. 

Baboon,  317. 

Babyroussa,  299. 

Badger,  308. 

Balcena,  295. 

Ealcenidce,  295. 

Balancers,  158. 

Balanidce,  137. 

Balanus.  137. 

Bald  Eagle,  278. 

Baleen,  295. 

Balistidce,  220. 

Bandicoot,  291. 

Banxring,  315. 

Bascanion,  244. 

Batides,  223. 

Batrachia,  230. 

Bats,  312,  313. 

Beaver,  311. 

Bee-eaters,  277. 

Bees,  160. 

Belemnites,  192. 

Big-horn,  303. 

Bimana,  287 ;  general  characters  of,  319. 

Biology,  definition  of,  3. 

Bird-lice,  153. 

Birds  (see  Aves). 

Bird's-head  process,  171. 

Birds  of  Prey,  277. 


Bittern,  269. 

Bivalve  Shell-fish,  167, 176. 

Black -game,  272. 

Black  Snake,  244. 

Bladder-worms  (see  Cystic  Worms). 

Blastoidea,  105. 

Blattina,  155. 

Blind-worm,  245,  246. 

Boa,  244. 

Bombyx,  160. 

Bonasa,  272. 

Book-scorpion,  139. 

Bos,  303. 

Bovidce,  303. 

Box-tortoise,  240. 

Brachiopoda,  165,  167 ;  general  characters 

of,  174, 175. 
Brachyura,  132. 
Bracts  (Oceanic  Hydrozoa),  71. 
Bradypodida,  292. 
Branchial  hearts  (Cuttle-fishes),  189. 
Branchial  sac  (Tunicata),  172:  (Lancelot), 

215. 

Branchiate  Gasteropods,  182. 
Bubalu*,  303. 
Buccinum,  183. 
Buceridce,  276. 
Buffalo,  303. 
B-iifonidw,  232. 
Bullfinch,  276. 
Bunting,  276. 
Bustards,  269. 
Butterflies,  148,  159. 
Byssus  (of  Lamellibranchiatd),  177. 

Caducibranchiata  (Amphibia).  227,  229. 
Cfflca,  intestinal  (of  Birds),  260. 


gono- 


Ccecilia,  226,  227. 
Caiman,  248. 
Calamaries,  187,  190,  192. 
Calycophoridw,  70-72. 
Camelidce,  301. 
Camelopardatidce,  302. 
Campanularida,    68;    medusiform 

phores  of,  69. 
Canals,  of  Sponges,  41  ;  of  Alcyonaria,  90  ; 

of  Ctenophora,  94. 
Canidce,  808. 
Cantharis,  168. 
Capreolw,  302. 
Caprimulgidw,  277. 
Capybara,  311. 
Caribou,  302. 
Carinaria,  184,  185. 

Carnivora,  287  ;  general  characters  of,  803. 
Carriage-spring  apparatus  (Brachiopoda), 

175. 

Cassowary,  269,  271. 
Casuarius,  271. 
Castoridm,  311. 
Catarhina,  316. 
Cathartes,  278. 
Cats,  806.  309. 
' 


Cavicomia,  302. 

Cebidce,  316. 

Cellulose  in  Ascidians,  5,  172. 

Centetes,  315. 

Centipedes,  144,  145. 

Cephalaspis,  222. 

Cephalopoda,  165,  176;  general  characters 

of,  187;  respiratory  organs  of,  189;  shell 

of,  190  ;  reproduction  of.  189. 
Cephalothorax,  128,  139. 
Cerastes,  245. 
Certhidoe,  276. 
Cervidce,  301. 
Cervus,  302. 
Cestraphori,  223. 
Cesium,  94. 

Cetacea,  287  ;  general  characters  of,  294. 
ChoEtognatha,  119. 
Chameleo,  247. 
Chamois,  303. 
Charadriidce,  269. 
Cheiromys,  316. 
Cheiroptera,    287;    general    characters  of, 

312. 

Cheirotheriwn,  233. 
Chete,  131. 
Chelydra,  240. 
Chelifer,  142. 

Chelonia,  237;  general  characters  of,  238. 
Chimara,  222,  223. 
Chimpanzee,  318. 
Chitine,  61. 
Cldamyphorus,  292. 
Chlorophyll,  in  Animals,  5. 
Chrysochloris,  314. 
Cicada,  154. 

Ciliata  (Infusoria),  49. 
Cirripedia,  136. 
Cistudo,  240. 
Civet,  308. 
Cladocera,  135,  136. 
Clamatores,  273. 
Classification,  6,  14 
Cleodora,  186. 


366 


INDEX. 


Cliona,  43. 

Cloaca,  of  Rotifera,  117;  of  Insects,  149;  of 

Amphibia,  225;  of  Reptiles,  236:  of  Birds, 

260;  of  Monotremes,  288. 
Clupeidce,  219. 
Coati,  308. 

Cochineal  Insects,  154. 
Cockroaches,  155. 
Cocoon,  152. 
Cozlenterata,  15 ;  general  characters  of,  50- 

52 ;  thread -cells  of,  52 ;  divisions  of,  52. 
Ccenosarc,  56. 
Coleoptera,  162, 163. 
CoUosphcera,  39,  40. 
Colobus,  317. 
Coluber,  244. 
Columbacei,  271-273 
Comatula,  104,  105. 
Condor,  279. 
Condylura,  314. 
Conirostres,  276. 

Contractile  vesicle,  of  Protozoa,  26 ;  of  Amoe- 
ba, 31;  of  Infusoria,  47. 
Coot,  269. 

Copepoda,  135, 136. 
Copperhead  Snake,  244. 
Coral,  88. 
Corallite,  88. 
Corattium,  91. 
Corallum,  86,  88. 
Coral-reefs,  88,  89. 
Cordylophora,  60,  62. 
Corncrake,  269. 
Corynida,  57;  general  characters  of,  60,  61 ; 

reproduction  of,  62,  63. 
Coryomorplia,  62. 
Coturnix,  272. 
Cracidce,  272. 
Crane,  269. 
Crane-fly,  158. 
Craspeda,  87. 
CribeUa,  100, 101. 
Crinoidea,  96;  general  characters  of,  103- 

105. 

Cristatella,  171. 
Crocodilia,  237 ;  general  characters  of,  247, 

248. 

Crop,  of  Insects,  148;  of  Birds,  260. 
Cross-bill,  276. 
CrotalidoE,  244. 
Crotalus,  244. 
Crow,  276. 

Crustacea,  127;  general  characters  of,  128. 
Ctenophora,  85;  general  characters  of;  93,  94. 
Ctenophores,  93. 
Cuckoo,  273. 
Cuculidce,  273. 
Culex,  159. 
Curassow,  272. 
Curlew,  269. 
Cursores,  265,  269. 
Cuticle,  of  Infusoria,  46. 
Cuttle-fishes,'  166, 187-190. 
Cuvieria,  186. 
Cyamm,  138. 
Cyanea,  80. 
~z«,  178. 

'  ibridce,  219. 
ops,  136. 
lime,  ' 

,267. 


,thia,  172. 
Cyprinidce,  219. 
Cypris,  136. 
CypselidoB,  277. 
Cystic  Worms,  109,  111,  112. 
Cystoidea,  96, 105. 

Daphnia,  136. 
Dasypodidce,  292. 
Dasyprocta,  311. 
Dasyurus,  291. 

Decapoda     (Crustacea),    129;    (Cephalo- 
poda), 191, 192. 
Deer,  301. 

Deinosauria,  237,  252. 
DelpMnidce,  296. 
Dental  formula,  283. 
Dentirostres,  276. 
Desmidice,  5. 
Diatomacece,  5. 
Dibranchiata,  189,  190, 192. 
Dicotyle*,  299. 
DidelpMdce,  290,  291. 
Didelphys,  291. 
Difflugia,  32,  36. 
Difjitigrada,  306,  308. 

Dipnoi,  214 ;  general  characters  of,  223. 

Dipodidcc,  311. 

Diptera,  158. 

Discophora  (Medusa),  57,  74,  75,  77. 

Discorbina,  33-35. 

Diatom  a,  112. 

Diver,  267. 

Dodo,  273. 

Dog,  308. 

Dolphin,  296, 


Dormice,  311. 

Dorsal  vessel  of  Insects,  149. 

Draco,  246,  251. 

Dragon-flies,  156. 

Dromaius,  270. 

Dromedary,  301. 

Duck,  267. 

Duck-mole,  288. 

Dugong,  293,  294. 

Eagle,  278. 

Echidna,  288,  289. 

EcMnodermata,  95;  general  characters  of, 

96. 
Echinoidea,  96 ;   general  characters  of,  97 ; 

aquiferous  system  of,  98 ;  development  of, 

100. 

EchinorJiynclius,  114. 
Echinus,  anatomy  of,  97-99. 
Ectocyst,  168. 
Ectoderm,  50,  52,  84. 
Edentata,  general  characters  of,  291. 
Egret,  269. 
Elaps,  245. 
ElasmobrancJiii,  214 ;  general  characters  o£ 

221 ;  sub-orders  of,  223. 
Elephant,  304,  305. 
Elephant-shrew,  314. 
Elk,  301. 
Elytra,  163. 
Emeu,  270. 
Emydidop,  240. 
Emys,  239. 


INDEX. 


367 


Endocyst,  168. 
Endoderm,  50,  52,  84. 
Entozoa,  108. 
Eozoon,  37. 
Ephemeridfp,  156. 
JSpistylis,  46,  48. 
EquidcK,  298. 
Erinaceidcp,  314. 
EHnaceus,  315. 
Ermine,  308. 
Errantia,  121, 124. 
Esocidce,  219. 
Eudendrium,  61. 
Euplectella,  42. 
Eurypterida,  134. 
Eyes  of  Insects,  149. 

Feather-star,  104. 

Felidce,  306.  309. 

Field-bug,  154. 

Filaria.  115. 

Finches,  276. 

Finner-whales,  295. 

Fission,  continuous  and  discontinuous,  54. 

Fissirostres,  276. 

Flagellata  (Infusoria),  49. 

Fleas,  158. 

Flesh-flies.  159. 

Float,  of  PhysophoridcB,  72. 

Flukes,  112. 

Flustra,  4, 170. 

Fly-catcher,  276. 

Flying  dragon,  246. 

Flying-lemur,  315. 

Flying  squirrel,  311. 

Food  of  animals  and  plants,  5,  6. 

Food-vacuoles,  47. 

Foot,  of  Mollwca,  166, 177, 181,  184, 186, 1S7. 

Foot-jaws,  130. 

Foot-tubercles,  120. 

Foraminifera,  26, 29, 30 ;  general  characters 
of,  33 ;  pseudopodia  o£  33 ;  shell  of,  34 ;  af- 
finities of,  36 ;  distribution  of,  in  space,  37 ; 
in  time,  37;  presence  of,  in  white  chalk, 

Forest-flies,  159. 
Formica,  162. 
Formicidce,  160. 
Fowl,  272. 
Fox-bats,  313. 
Frigate-birds,  267. 
Fringittidce,  276. 
Fringing-reefs,  89. 

Frog,  230,  232;  development  of,  231. 
Fulica,  269. 

Funnel,  of  Ctenophora,  94;  of  Cephalopo- 
da, 188;  of  Nautilus,  188, 192. 

Gad-flies,  159. 

Gadidm,  219. 

Galeopithecu^  315. 

Gallinacei,  271. 

Gallinula,  269. 

Gallm.  272. 

Gammarus,  138. 

Gannet,  261,  267. 

Ganoidei,  214;  general  characters  of,  220. 

Gasteropoda,   165,  176;  general  characters 

of,  180;  shell  of,  182  ;  odontophore  of,  181 ; 

development  of,  182. 
Gavial,  248. 


Geckotida,  246. 

Geese,  267. 

Gemitores,  273. 

Gemmation,  continuous  and  discontinuous, 

54. 

Gemmules  of  Spongilla,  43. 
Gemsbok,  303. 

Generations,  alternation  of,  64,  65. 
Genette,  308. 
Gephyrea,  119. 
Gibbon,  318. 
Giraffe,  302. 

Gizzard,  of  Insects,  148;  of  Birds,  260. 
Glass-snake,  245. 
Globigerina,  34,  36. 
Glutton,  308. 
Gnats,  159. 
Gnu,  303. 
Goat,  303. 
Goat-sucker,  277. 
Gobiidce.  219. 
Golden  mole,  311. 
Goniaster,  101. 

Gonophores,  63,  64;  medusiform,  65,  68. 
Gonosome,  63. 

Gordiacea,  109 ;  characters  of,  114. 
GorgonidcK,  91,  92. 
Gorilla,  318,  319. 
Grallatores,  265,  267. 
Graptolitidffi,  82. 
Grasshoppers,  155. 
Grebe,  267. 

Greenland  Whale,  295. 
Gregarina,  28. 

Gregarinidce,  27 ;  reproduction  of,  28. 
Grosbeak,  276. 
Gruidce,  269. 
GrylUna,  155. 
Guan,  273. 
Guillemot,  267. 
Guinea-fowl,  272. 
Guinea-pig,  311. 
Guinea-worm,  115. 

Guio,  soa 

ffcemopsis.  122. 

Hag-fishes,  216. 

Hair-worms.  114. 

Ilalicore.  293,  294. 

Halietm,  278. 

Halteres  (see  Balancers). 

Hamster,  310,  311. 

Hapalidce,  316. 

Hare,  311. 

Harlequin  Snake,  245. 

Harvest  Spiders,  142. 

Hawks,  277,  278. 

Hectocotylus.  190. 

Hedgehog,  815. 

Hemelytra,  154. 

Hemimetabolic  Insects,  150, 154. 

Hemiptera,  154. 

Hermit-crabs.  131. 

Heron,  268,  269. 

Heteropoda,  184. 

Hippobosca,  159. 

Hippocampida,  220. 

Hirudinea,  121 ;  general  characters  of,  121, 

122. 

Hirundinida,  277. 
Holocephali,  223. 


368 


INDEX. 


Holometabolic  Insects,  150, 153. 

Hololhuroidea,  96;  general  characters  of, 
106. 

Homology,  14, 15. 

Honey-badger,  308. 

Honey-eater,  276. 

Hoopoe,  276. 

Hornbill,  261,  276. 

Horse,  298. 

Horseshoe  Crab,  133, 134. 

House-fly,  159. 

Humming-birds,  276. 

Hycenida,  309. 

Hydatids,  112. 

Hydatina,  116. 

Hydra,  53,  56-59 ;  reproduction  of,  60. 

Ifydrachna,  141. 

Hydra-tuba,  80. 

Hydrida,  57. 

Ilydroida,  57,  66 ;  reproduction  of,  62-66. 

Hydroid  Zoophytes,  53,  59. 

llydrophidai,  244. 

Hydrosoma,  56. 

Hydrotheca,  66,  67. 

Jfydrozoa,  characters  of,  52, 53 ;  terminology 
of;  53,56;  reproduction  of,  62,  66;  divis- 
ions of,  57. 

Hylobates,  318. 

Ilymenoptera,  160. 

Hyracoidea,  287 ;  general  characters  of,  303. 

Hyrax,  304. 

Hystricidce,  311. 

Ibis,  269. 

Ichneumon,  160. 

Ichthyomorpha,  227. 

Ichthyophthira,  138. 

Ichthyopsida,  204. 

Ichthyopterygia,  237;  cLaracters  of,  249. 

Ichthyosaurus,  249. 

Iguana,  246. 

Ilyanthus,  87. 

Imago,  150, 151. 

Imperforata  (Foraminifera),  35. 

Individual,  definition  of,  53-55. 

Infusoria,  27,  45 ;  general  characters  of,  46 ; 
distribution  of,  in  space,  49. 

Insecta,  127;  general  characters  of,  146;  or- 
gans of  the  mouth  of,  147;  digestive  sys- 
tem of,  148;  metamorphoses  of  150;  orders 
of;  153-163. 

Insectivora,  287;  general  characters  of,  313, 
314. 

fnsessores,  265,  274. 

Invertebrates,  general  characters  of,  15,  16, 
196. 

Isis,  91,  92. 

Isopoda,  133. 

lulus,  145. 

Jaguar,  309. 
Jelly-fishes,  64,  65,  74. 
Jerboa,  811. 
Jumping-mouse,  811. 
Jungle-fowl,  272. 

Kangaroo,  290,  291. 
Kangaroo-bear,  290,  291. 
King-crab,  133, 134. 
Koodoo,  303. 


Labium,  148. 

Labrum,  147. 

Labyrinthodontia,  226,  232. 

Lacerta,  245. 

Lacertilia,  237;  general  characters  of,  245. 

LcBtnodipoda,  138. 

Lagena,  34,  35. 

Lagopus,  272. 

LamellibrancJiiata,  165, 174 ;  general  char- 
acters of,  176;  shell  of,  178;  respiration  of, 
179;  habits  of,  180. 

Lamprey,  216,  217. 

Lamp-shells,  167, 174. 

Lancelot,  197,  203,  204,  212. 

Land-salamanders,  229,  230. 

Laniidce,  276. 

Lapwing,  269. 

Laridw,  267. 

Larks,  276. 

Larva  (of  Insects),  150, 151. 

Leeches,  121,  122. 

Lemming,  811. 

Lemurs,  316. 

Leopard,  309. 

Lepadidce,  137. 

Lepidoptera,  159. 

Lepidosiren,  212,  213,  216,  223,  224. 

Lepidostem,  220. 

Leporidce.  311. 

Lemoe,a,  138. 

LibellulidoK,  156. 

Lice,  153. 

Limulus,  134. 

Lingual  ribbon  (of  Mollwca),  181, 182. 

Lingula,  174, 175. 

Lion,  309. 

Liver-fluke,  112. 

Lizards,  245. 

Lobster,  129, 130. 

Lob-worm,  124,  125. 

Locustidoe,  155. 

Lophobranchii,  220. 

Lophopus,  170. 

Lophortyx,  272. 

Lories,  274. 

Lucernaria,  78. 

Lucernarida,  characters  of,  78;  develop- 
ment  of,  79,  80 ;  structure  of  reproductive 
zotiids  of,  80-82. 

Lumbricidce,  122. 

Lurribricus,  123. 

Lynx,  309. 

Macaque,  317. 

Maccaw,  274. 

Macropodidce,  290. 

Macroscelides,  314. 

Macrura,  129. 

Madreporiform  tubercle,  of  Echinus,  98;  of 
Star-fishes,  101 ;  of  Holothurians,  106. 

Malacodermata  (Zoantharia),  86. 

Malacopteri,  219. 

Mallophaga,  153. 

Malpighian  vessels,  of  Insects,  149. 

Mammalia,  205;  general  characters  of.  280; 
skeleton  of,  281;  teeth  of,  282;  digestive 
system  of,  201 ;  circulatory  system  of,  284 ; 
respiratory  system  of,  285  $  nervous  system 
of,  285;  integumentary  system  of,  286; 
orders  of,  287. 

Mammoth,  305. 


INDEX. 


369 


Manatee,  298. 

Manis,  286. 

Mantle,  167, 175, 176, 179, 188. 

Manubrium,  64,  65,  68,  76. 

Marginal  bodies,  of  Medusidce,  76 ;  of  Lu- 
cernarida,  81. 

Marmoset,  315. 

Marmot,  312. 

Marsipobranchii,  214;  characters  of,  216. 

Marsupialia,  287 ;  characters  of,  289. 

Marten,  277. 

May-flies,  156. 

Measles,  of  pig,  111. 

Medusae,  naked-eyed,  74,  76;  hidden-eyed, 
74,  81. 

Medusidce,,  74,  75. 

Medusoid  buds,  of  Hydrozoa,  64,  65,  68,  76. 

Megapodidce,  272. 

Meleagris,  272. 

Meles,  308. 

Melicerta,  116. 

Meliphagidce,  276. 

Mephitis,  808. 

Meropidcz,  277. 

Merostomata,  133. 

MeruUdoB,  276. 

Mesenteries,  of  Actinosoa,  84,  87. 

Metamorphoses  of  Insects,  150, 151. 

Mice,  311. 

Miliola,  33,  34,  3T. 

Millipedes,  144, 145. 

Mink,  308. 

Mites,  141. 

Modeeria.  75. 

Mole,  314. 

Mollusea,  15;  general  characters  of,  164; 
shell  of,  166;  divisions  of,  167. 

Mollusea  Proper,  characters  of,  167:  di- 
visions of,  176-194. 

Molluscoida,  characters  of,  167;  divisions 
of,  168-175. 

Monera,  29. 

Monitors,  246. 

Monkeys,  315. 

Monothalamous  shells  (Foraminifera),  35. 

Monotremata.  287 ;  characters  o$  288. 

Moose,  301. 

Morphology,  10. 

Morse,  807. 

Moths,  159, 160. 

Mound-birds,  272. 

MugilidcK,  219. 

Multivalve  shells,  167, 182. 

Murcenidce,  219. 

Muridae,  311. 

Musca,  159. 

Muscicapidce,  276. 

Musk-ox,  303. 

Musquash,  311. 

MusteUdoR,  308. 

Mya,  177, 180. 

Mycetes,  316. 

Myoxidw,  311. 

Myriapoda,  127 ;  general  characters  of,  144. 

Myrmecophaga,  292. 

Myrmeleo,  156. 

Myxine,  216. 

Myxinidce,  216. 

Myxinoids,  213,  216,  224, 

Naididae,  122, 123. 


Naja,  244,  245. 

Narwhal,  296. 

Namta,  308. 

Natatores,  265;  characters  of,  266. 

Nautiloid  shells  (Foraminifera),  86. 

Nautilus,  Pearly,  187-190,  192,  193;  Paper, 

187, 188,  190,  191. 
Nectocalyces,  70,  71. 

Nematoda,  109 ;  general  characters  of,  114. 
NemertidcK,  113. 
Nervures,  146. 
Newoptera,  156. 
Night-heron,  269. 
Noctiluca,  49. 
Nodosaria,  34,  85. 
Nucleolus,  of  Paramoecitvm,  47. 
Nucleus,  of  Protozoa,  26 ;  of  Amoeba,  32 ; 

of  Paramoecium,  47. 
Nitdibranchiata,  184. 
Jfiimenius,  269. 
Numida,  272. 
Nummulites,  37,  88. 
Nummulitic  Limestone,  87. 
Nycticebidce,  316. 

Oceania  Hydrozoa,  70. 

Octopoda,  188, 191. 

Octopus,  191. 

Odontoeeti,  295. 

Odontophore,  165, 181, 186, 188. 

Oligochceta,  121 ;  characters  of,  122. 

Omnivora  (Ungulatd),  298. 

Oniscus,  133. 

Operculum  (of  MoUusks),  181;  (of  Fishes), 

Ophidia,  237;  characters  of,  241-244. 

Ophiocoma,  102. 

Ophiomorpha,  226. 

Ophisaurus,  245. 

Ophiura,  102. 

Ophiuroidea,  96;  characters  of,  101-103. 

Opossum,  290,  291. 

Orang-outan,  818. 

Organ-pipe  Coral,  91. 

Organs  of  the  mouth  of  Insects,  147. 

Ornithorhynchus,  288,  289. 

Orthoceras,  193, 194. 

Orthoptera,  155. 

Ortyx,  272. 

Orycteropus,  293. 

Oscula,  of  Sponges,  41,  42. 

Osteolepis,  221. 

Ostraciontidce,  220. 

Ostracoda,  135, 136. 

Ostrich,  254,  258,  269,  270. 


Otter,  308. 

Ovarian  vesicles,  of  Sertularida,  68. 


Ovidce,  303. 
Ovipositor,  147, 160. 
Ovis,  303. 
Owls,  278. 
Oxen,  303. 
Owyuris,  115. 
Oyster-catcher,  269. 

Paca,  311. 
Paguridce,  131. 
Pallial  line,  178, 179. 
Pallial  sinus,  179. 


370 


INDEX. 


Pallium  (see  Mantle). 

Pangolin,  293. 

Paper  Nautilus,  187,  188,  190,  191. 

Paramoecium,  46,  47. 

Parapodia,  120. 

PartdcB,  276. 

Parrakeets,  274. 

Parrots,  259,  273. 

Partridge,  272. 

Passerine  Birds,  274. 

Patagium,  812. 

Panropus,  145. 

Pavo,  212. 

Pea-fowl,  272. 

Pearly  Nautilus,  187-190,  192,  193. 

Peccary,  299. 

Pecten,  180. 

Pedicellariae,  of  Echinus.  98:  of  Star-fishes, 

101. 

Pedipalpi,  141. 
Pelia*,  244. 
Pelicanus,  267. 
Peltogaster,  138. 
Penguin,  266,  267. 
Pennatula,  91. 
Pentatoma,  154. 
Perameles,  291. 
Perchers,  274. 
Percidce,  219. 
Perdicidoe,  272 

Perennibranchiata  (Amphibia),  227. 
Perforate,  (Foraminiferd),  35. 
Perissodaetyla,  297. 
Petromyzon,  217. 
PetromyzonidiK,  216. 
Phacochoerus,  299. 
Phalacrocorav,  267. 
Phalangers,  291. 
Phalangidce,  142. 
Phalangista,  291. 
PliaryngobrancliH,  214. 
Pharynx  (of  Ascidians),  174;    of  Lancelet, 

215. 

Phascolarctos,  290,  291. 
Phasianidce,  272. 
Pheasants,  272. 
Pholades,  180. 
Phryganeidce,  156. 
Phyllopoda,  138. 
Phyllostomidce,  312. 
Physalia,  53,  72. 
Physiology,  10. 
Physoplioridce.  72. 


Pigeons,  271-273. 

Pinnigrada,  306,  307. 

Pipidce,  232. 

Pisces,  204;  general  characters  of,  206; 
scales  of,  206;  skeleton  of,  207;  limbs  of, 
208;  tail  of,  210;  digestive  system  of,  210; 
respiratory  system  of,  211  ;  heart  of,  212  ; 
swim-bladder  of,  213  ;  nervous  system  of, 
213;  reproduction  of,  213;  orders  of,  214- 

Placental  Mammals,  286,  287. 
Plagiostomi,  223. 
Planarida,  113. 
Plantigrada.  306,  308. 
Platyrhina,  315. 
Plectognathi,  220. 
Plesiosaurus,  250. 


Pleurdbrachia,  93. 

Pleuronectidce,  219. 

Pluteus,  100. 

Pneumatophore,  72.  . 

Podosomata,  140. 

Podura,  154. 

Pole-cat,  308. 

Polycystina,  86 ;  characters  of,  33. 

Polygastriea,  47. 

Polynoe,  125. 

Polypary,  56. 

Polype,  85. 

Polypide,  168. 

Polypidom,  56. 

Polypite,  56. 

Polypterus,  220,  221. 

Polythalamia  (Foraminifera},  35. 

Polyzoa,  165,  167 ;  characters  of,  168-171. 

Porcupine,  286. 

Pores,  of  Sponges,  41,  42, 

Porpoise,  296. 

Portuguese  Man-of-war,  53, 72. 

Poulpes,  191. 

Prairie-dog,  312. 

Proboscidea,  287;  characters  of,  304. 

Procellaridct',  267. 

Procyon,  308. 

Prong-buck,  303. 

Proteus,  227,  228. 

Proteus-anknalcule,  30. 

Protophyta,  4. 

Protoplasm,  8. 

Protozoa,  4, 15;  characters  of,  25-27 ;  classi- 
fication of,  27. 

Proventriculus  of  Birds,  260. 

Pseudohaemal  System,  121. 

Pseudo-hearts.  175. 

Pseudonavicellse,  28. 

Pseudopodia,  of  Protozoa,  27;  of  EMzopo- 
da,  29;  ofAmo&ba,  80;  of  Foraminifera^ 
33;  ofJRadiolaria,3$. 

Psittacidce,  273. 

Ptarmigan,  272. 

Pterodactyles.  251. 

Pteropidce,  313. 

Pteropoda,  166 ;  characters  of,  186. 

Pteropus,  313. 

Pterosauria,  237;  characters  of,  250. 

Pterygotm,  134. 

Pulicidce,  158. 

Pulmonary  sacs  (Arachnida),  140. 

Pulmonate  Gasteropoda,  182, 185. 

Puma,  309. 

Pupa,  150, 151. 

Pycnogonum,  141. 

Python,  235,  244. 

rdrwnana,  287;  characters  of,  815. 
?a,  298. 
272. 

Rabbit,  311. 

Eaccoon,  308. 

Radiata,  50. 

RadioJana.  29 ;  characters  of,  88, 89. 

Rail,  269. 

Rallidai,  269. 

Ranidce,  232. 

Raptores,  266 ;  characters  of,  276. 

Rasores,  265;  characters  of,  271. 

Rat,  311. 


INDEX. 


371 


Eattlesnake,  244. 

Bed  Coral,  92. 

Bed  Deer,  302. 

Regnum  Protisticum,  4. 

Keindeer,  301. 

Eeproduction,  general  features  of,  53,  54 ;  in 
Hydroid  Zoophytes,  C2-66. 

Reptilia,  205;  characters  of,  234;  jaw  of, 
235;  teeth  of,  235;  circulation  of,  236;  res- 
piration of,  23T;  orders  of,  237. 

Eespiratory  tree,  of  Holothurians,  10T. 

Kespiratory  tubes,  of  Rotifera,  117. 

Rhea,  269,  270. 

Rhinoceros,  297,  298. 

Rhizocephala,  138. 

Rhizocrinus,  104, 105. 

Rhizopoda,  27 ;  characters  of,  29 ;  divisions 
of,  29. 

Rhizostoma,  82. 

Rhizostomidce,  82. 

Rhytina,  294. 

Eibbon-worms,  113. 

Rodentia,  287 ;  characters  of,  309,  310. 

Eoe-buck,  302. 

Eorqual,  295. 

Rotifera,  109;  characters  of,  115. 

Eound-worms,  114. 

liuffed  Grouse,  272. 

Rugosa,  92. 

Ruminantia,  298,  299;  dentition  of,  299; 
stomach  of,  300 ;  fomilies  of,  301. 

Sable,  308. 
Sagitta,  119. 
Salmonidce,  219. 
Sandpipers,  269. 

Sarcode.  26. 

Sarcoids,  of  Sponges,  41. 
Sarcorhampus,  279. 
Sauropsida,  205. 

Sauropterygia,  237;  characters  of,  250. 
Saururce,  266,  280. 
Saw-flies,  160. 
Scalops,  314. 

Scansores,  265:  characters  of,  273. 
Scincus,  246,  247. 
Sciuridce,  311. 

Sclerobaaica  (Zoantliaria\  90. 
Sclerobasic  Corals,  88,  91,  92. 
Sclerodermata  (Zoantharia*),  87. 
Sclerodermic  Corals,  88,  91,  92. 
Scoleeida,  95;  characters  of,  108. 
Scolopaddce,  269, 
Scolopendra,  145. 
8comberida>,  219. 
Scorpion,  141, 142. 
Sea-anemones,  86. 
Sea-cucumbers,  106. 
Seals,  306,  307. 
Sea-mosses,  167, 168. 
Sea-mouse,  124, 125. 
Sea-slugs,  184. 
Sea-spiders,  140. 
Sea-squirts,  165, 171. 
Segmental  organs  of  Annelides,  121. 
Selachii,  223. 
jSemnopithecufi,  316. 
Serpvla,  123, 124. 

Sertularida,  57,  61 ;  characters  of,  66 ;  poly- 
pites  of,  66;  reproduction  of,  67. 


Sheep,  303. 

Shell,  of  Foraminifera,  84;  of  Mollwca, 
166,  of  Brachiopoda,  174;  of  LamelU- 
branchiata,  178;  of  Gasteropoda,  182;  of 
Ifeteropoda,  185;  of  Pteropoda,  186 ;  of 
the  Argonaut,  190, 191 ;  of  Pearly  Nautilus, 
190, 192. 

Shrew-mice,  314. 

Silk-moth,  160. 

Siluridce,  219. 

Simla,  318. 

/Siphonophora,  57 ;  characters  of,  70. 

Siphons,  of  LamellibrancJiiata,  174, 179. 

Sipunculus,  120. 

Siren,  227,  228. 

Sirenia,  287;  characters  of,  203. 

Skink,  246,  247. 

Skunk,  308. 

Sloths,  292. 

Slow-worm,  245. 

Snakes,  201,  235. 

Snapping-turtle,  240. 

Snipes,  269. 

Soft-tortoises,  240. 

Solaster,  101. 

Slien,  180. 

Somatic  cavity,  of  Cml&nterata,  51,  84. 

Sorex,  314. 

Soricidce,  314. 

Spatularia,  221. 

Sperm-whale,  295. 

Spfieniscidw,  267. 

Spider-monkeys,  316. 

Spiders,  139,  140, 142. 

Spinneret,  of  Spiders,  143;  of  Caterpillars, 
159. 

Spirorbis,  124. 

Spongida,  29 ;  characters  of,  36;  aquiferous 
system  of,  41;  reproduction  of,  43;  dis- 
tribution of,  in  space,  43. 

Spongilla,  42 ;  reproduction  of,  43. 

Spoon-bill,  269. 

Spoon-worm,  120. 

Spring-bok,  303. 

Spring-tails,  153. 

Squids,  187, 190, 192. 

Squilla,  138. 

Squirrel,  311. 

Star-nosed  Mole,  814. 

Stentor,  5,  48,  49. 

Stephanoceros,  116. 

Stomapoda,  138. 


StrepsirMna,  816. 
Strepsiptera,  162. 
Strigidce,  278. 
Struthio,  270. 
Sturgeon,  220,  221. 
Sturio,  220. 
Sturionidaz.  221. 
Sub-kingdoms,  11,  15. 
Suctoria  (Infusoria),  49. 
* 


Surinam  Toad,  232. 


Swallows,  277. 
Swifts,  258,  277. 
Swim-bladder,  of  Fishes,  218. 
Swimming-bells,  70,  71. 
Syngnathidce,  220. 
Syrinx,  120. 


372 


INDEX. 


Tabanidce,  159. 

Tcenia,  109,  111. 

Tceniada,  108;  characters  of;  109;  develop- 
ment of,  110,  111. 

Talitrus,  138. 

Talpidce,  314. 

Tanagers,  276. 

Tantalince,  269. 

Tape-worm,  109-111. 

Tapir,  297. 

Teleostei,  characters  of,  217-219;  sub-orders 
of;  219,  220. 

Tenrec,  315. 

Tenthredinidw,  160. 

Termites,  156, 157. 

Terrapin,  240. 

Test,  of  Foraminifera,  34;  of  Echinoid ea, 
97 ;  of  Tunicata,  172. 

Testudo,  241. 

Tetrabranchiata,  189, 192, 193. 

Tetranychw,  141. 

Tetrao,  272. 

Tetraonidte,  272. 

Thala&ricolla,  39,  40. 

ThalassicoUida,  39. 

Theriomorpha,  230. 

Thick-knee,  269. 

Thread-cells,  52. 

Thread-worms,  114. 

Tfiylacinus,  291. 

Tkysanura,  153. 

Ticks,  140, 141. 

Tiger,  309. 

Tipula,  158. 

Tits,  276. 


Tongue,  of  Gasteropods,  181 ;  of  Cuttle-fish- 
es, 188;  of  Snakes,  242;  of  Birds,  '25J. 
Tortoises,  235,  236,  238,  240. 
Tracheae,  140, 149. 
Tree-frog,  230,  232. 
Trematoda,  108;  characters  of,  112. 
Trichecus,  307. 
Trichina,  115. 
Trigonocephalus,  244. 
Trilobita,  135. 
Tringidce,  269. 
Trionycidce,  240. 
Triton,  229. 
TrochiUdce.  276. 
Troglodytes.  818. 
Troffonidce,  274. 
Trophosome,  63. 
Tube-feet  of  Echinus,  98,  99. 
Tubicola,  121, 123. 
TfoW/w,  123. 
Tubipora,  91. 
Tubularia,  61. 
Tutntlarida  (see  rori/nida). 
Tunicata.  165, 167;  characters  of,  171, 172. 
Tupaia,  815. 
Twrbellaria,  108;  characters  of,  113. 


Turkey,  272. 
Turn-stone,  269. 
Turritella,  183. 
Turtles,  235,  236,  238,  239. 

Umbo,  178. 

Umbrella,  of  Lucemarida,  78,  80-82. 

Univalve  Shells,  167, 180, 182. 

Ungulata,  287 ;  characters  of,  296. 

Upupince,  276. 

Uraster,  101. 

Urodela,  226,  227. 

Ursidce,  308. 

Vacuoles,  of  ^i«?CB&a,  31 ;  of  Paranuxciwm., 

Vaginicola,  48,  49. 
Valkeria,  170. 
Vampire-bats,  313. 
Varanidce,  246. 
Veil,  of  gonophores,  64,  68 ;  of  nectocalyces, 

71 ;  of  naked-eyed  Medusa,  76. 
Velella,  72,  73. 
Venus's  Flower-basket,  42. 
Venus's  Girdle,  94. 
Vermes,  119. 

Vertebra,  structure  of,  197, 198. 
Vertebrata,  195;  general  characters  of,  195; 

skeleton  of,  197-201 ;  digestive  system  of, 

201;    blood  of,  202;  respiration  of,  203; 

nervous  system  of,  204;  reproduction  of, 

204;  divisions  of,  204.  205. 
Vesicle,  contractile,  of  Protoeoa,  26. 
Vespidce,  160. 
Viperidce,  244. 
Virgularia,  90. 
Viverridce,  808. 
Vorticella,  48,  49. 
Vulture,  278. 

Wah,  30a 

Walrus,  807. 

Wapiti,  802. 

Warblers,  276. 

Wasps,  160. 

Water-hens,  269. 

Water-vascular  system,  95,  96. 

Weasel  808. 

Wolf,  308. 

Wolverine,  308. 

Woodcock,  269. 

Woodpeckers,  273. 

Wren,  276. 

Xiphosura,  133. 

Zoantharia,86',  Mala cod ermata,  86;  Sole- 

robasica.  90 ;  sclerodermata,  87. 
Zoanthm,  87. 
Zooid,  55. 
Zoology,  definition  of,  3. 


THE    END. 


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